Docs for MXRecordIO, MXIndexedRecordIO modified (#6013)
Docs for MXRecordIO, MXIndexedRecordIO modified (#6013)

* docs for MXIndexedRecordIO modified

* changes after review

* recordIO doc modified

* changes after review

* lint error

* minor change

* minor change after review

* empty commit to retrigger build

* changes after review

mbaijal/incubator-mxnet,eric-haibin-lin/mxnet,gautamkmr/incubator-mxnet,stefanhenneking/mxnet,ptrendx/mxnet,hpi-xnor/BMXNet,solin319/incubator-mxnet,jamesliu/mxnet,apaleyes/mxnet,yuruofeifei/mxnet,jennyzhang0215/incubator-mxnet,arikpoz/mxnet,fullfanta/mxnet,precedenceguo/mxnet,jiajiechen/mxnet,reminisce/mxnet,kevinthesun/mxnet,ShownX/incubator-mxnet,Mega-DatA-Lab/mxnet,arank/mxnet,smolix/incubator-mxnet,rishita/mxnet,ptrendx/mxnet,dmlc/mxnet,danithaca/mxnet,pluskid/mxnet,Prasad9/incubator-mxnet,dmlc/mxnet,piiswrong/mxnet,formath/mxnet,ShownX/incubator-mxnet,coder-james/mxnet,formath/mxnet,TuSimple/mxnet,luoyetx/mxnet,stefanhenneking/mxnet,smolix/incubator-mxnet,TuSimple/mxnet,gautamkmr/incubator-mxnet,Prasad9/incubator-mxnet,sxjscience/mxnet,Mega-DatA-Lab/mxnet,DR08/mxnet,sergeykolychev/mxnet,szha/mxnet,hesseltuinhof/mxnet,kevinthesun/mxnet,tlby/mxnet,ykim362/mxnet,ptrendx/mxnet,thirdwing/mxnet,piiswrong/mxnet,tlby/mxnet,navrasio/mxnet,jiajiechen/mxnet,smolix/incubator-mxnet,apaleyes/mxnet,leezu/mxnet,ForkedReposBak/mxnet,nicklhy/mxnet,szha/mxnet,luoyetx/mxnet,solin319/incubator-mxnet,arank/mxnet,rishita/mxnet,xcgoner/dist-mxnet,Mega-DatA-Lab/mxnet,kkk669/mxnet,danithaca/mxnet,Ldpe2G/mxnet,mbaijal/incubator-mxnet,solin319/incubator-mxnet,danithaca/mxnet,xcgoner/dist-mxnet,vikingMei/mxnet,ShownX/incubator-mxnet,DR08/mxnet,mbaijal/incubator-mxnet,jennyzhang0215/incubator-mxnet,vikingMei/mxnet,antoan2/incubator-mxnet,ShownX/incubator-mxnet,navrasio/mxnet,navrasio/mxnet,ZihengJiang/mxnet,rahul003/mxnet,apaleyes/mxnet,rahul003/mxnet,LinkHS/incubator-mxnet,tornadomeet/mxnet,wangyum/mxnet,arank/mxnet,dmlc/mxnet,yajiedesign/mxnet,zhreshold/mxnet,navrasio/mxnet,kevinthesun/mxnet,zhreshold/mxnet,thirdwing/mxnet,LinkHS/incubator-mxnet,jermainewang/mxnet,kevinthesun/mxnet,saurabh3949/mxnet,ForkedReposBak/mxnet,sergeykolychev/mxnet,danithaca/mxnet,LinkHS/incubator-mxnet,leezu/mxnet,zhreshold/mxnet,DR08/mxnet,ykim362/mxnet,sergeykolychev/mxnet,yajiedesign/mxnet,hotpxl/mxnet,vikingMei/mxnet,saurabh3949/mxnet,CodingCat/mxnet,rahul003/mxnet,ShownX/incubator-mxnet,stefanhenneking/mxnet,sergeykolychev/mxnet,DR08/mxnet,thirdwing/mxnet,tornadomeet/mxnet,hesseltuinhof/mxnet,Prasad9/incubator-mxnet,hotpxl/mxnet,jiajiechen/mxnet,zhreshold/mxnet,EvanzzzZ/mxnet,rahul003/mxnet,jamesliu/mxnet,coder-james/mxnet,jermainewang/mxnet,szha/mxnet,ptrendx/mxnet,yuruofeifei/mxnet,szha/mxnet,thirdwing/mxnet,rishita/mxnet,madjam/mxnet,jamesliu/mxnet,LinkHS/incubator-mxnet,rahul003/mxnet,coder-james/mxnet,apaleyes/mxnet,arikpoz/mxnet,LinkHS/incubator-mxnet,reminisce/mxnet,solin319/incubator-mxnet,saurabh3949/mxnet,hotpxl/mxnet,ForkedReposBak/mxnet,larroy/mxnet,sxjscience/mxnet,tlby/mxnet,hotpxl/mxnet,apaleyes/mxnet,weleen/mxnet,TuSimple/mxnet,ZihengJiang/mxnet,Northrend/mxnet,yuruofeifei/mxnet,nicklhy/mxnet,vikingMei/mxnet,hpi-xnor/BMXNet,arikpoz/mxnet,TuSimple/mxnet,apache/incubator-mxnet,lxn2/mxnet,mbaijal/incubator-mxnet,arank/mxnet,hpi-xnor/BMXNet,danithaca/mxnet,TuSimple/mxnet,yuruofeifei/mxnet,jamesliu/mxnet,Northrend/mxnet,antoan2/incubator-mxnet,likelyzhao/mxnet,coder-james/mxnet,reminisce/mxnet,leezu/mxnet,Ldpe2G/mxnet,Northrend/mxnet,madjam/mxnet,sxjscience/mxnet,kkk669/mxnet,eric-haibin-lin/mxnet,kkk669/mxnet,Prasad9/incubator-mxnet,weleen/mxnet,tornadomeet/mxnet,yajiedesign/mxnet,DR08/mxnet,indhub/mxnet,larroy/mxnet,EvanzzzZ/mxnet,wangyum/mxnet,formath/mxnet,likelyzhao/mxnet,eric-haibin-lin/mxnet,indhub/mxnet,ForkedReposBak/mxnet,LinkHS/incubator-mxnet,jermainewang/mxnet,Northrend/mxnet,nicklhy/mxnet,reminisce/mxnet,wangyum/mxnet,larroy/mxnet,Prasad9/incubator-mxnet,thirdwing/mxnet,Ldpe2G/mxnet,antoan2/incubator-mxnet,jiajiechen/mxnet,solin319/incubator-mxnet,crazy-cat/incubator-mxnet,eric-haibin-lin/mxnet,vikingMei/mxnet,pluskid/mxnet,saurabh3949/mxnet,CodingCat/mxnet,solin319/incubator-mxnet,jennyzhang0215/incubator-mxnet,Mega-DatA-Lab/mxnet,EvanzzzZ/mxnet,coder-james/mxnet,saurabh3949/mxnet,nicklhy/mxnet,CodingCat/mxnet,szha/mxnet,ShownX/incubator-mxnet,jiajiechen/mxnet,tornadomeet/mxnet,pluskid/mxnet,fullfanta/mxnet,sxjscience/mxnet,dmlc/mxnet,jermainewang/mxnet,ptrendx/mxnet,gautamkmr/incubator-mxnet,LinkHS/incubator-mxnet,kevinthesun/mxnet,precedenceguo/mxnet,dmlc/mxnet,fullfanta/mxnet,stefanhenneking/mxnet,EvanzzzZ/mxnet,ykim362/mxnet,mbaijal/incubator-mxnet,larroy/mxnet,navrasio/mxnet,Northrend/mxnet,leezu/mxnet,precedenceguo/mxnet,indhub/mxnet,jennyzhang0215/incubator-mxnet,fullfanta/mxnet,gautamkmr/incubator-mxnet,ForkedReposBak/mxnet,tlby/mxnet,ForkedReposBak/mxnet,arank/mxnet,EvanzzzZ/mxnet,antoan2/incubator-mxnet,LinkHS/incubator-mxnet,arikpoz/mxnet,pluskid/mxnet,sergeykolychev/mxnet,coder-james/mxnet,kevinthesun/mxnet,hesseltuinhof/mxnet,hpi-xnor/BMXNet,hotpxl/mxnet,jennyzhang0215/incubator-mxnet,DickJC123/mxnet,nicklhy/mxnet,lxn2/mxnet,sxjscience/mxnet,tlby/mxnet,xcgoner/dist-mxnet,dmlc/mxnet,EvanzzzZ/mxnet,rishita/mxnet,CodingCat/mxnet,thirdwing/mxnet,Northrend/mxnet,likelyzhao/mxnet,danithaca/mxnet,hotpxl/mxnet,hpi-xnor/BMXNet,sergeykolychev/mxnet,nicklhy/mxnet,vikingMei/mxnet,jennyzhang0215/incubator-mxnet,saurabh3949/mxnet,Mega-DatA-Lab/mxnet,weleen/mxnet,hpi-xnor/BMXNet,wangyum/mxnet,piiswrong/mxnet,tornadomeet/mxnet,crazy-cat/incubator-mxnet,precedenceguo/mxnet,leezu/mxnet,larroy/mxnet,likelyzhao/mxnet,navrasio/mxnet,danithaca/mxnet,DickJC123/mxnet,formath/mxnet,vikingMei/mxnet,formath/mxnet,TuSimple/mxnet,kevinthesun/mxnet,ykim362/mxnet,szha/mxnet,jiajiechen/mxnet,rahul003/mxnet,yajiedesign/mxnet,tornadomeet/mxnet,fullfanta/mxnet,saurabh3949/mxnet,Ldpe2G/mxnet,fullfanta/mxnet,gautamkmr/incubator-mxnet,nicklhy/mxnet,antoan2/incubator-mxnet,sxjscience/mxnet,jiajiechen/mxnet,xcgoner/dist-mxnet,ZihengJiang/mxnet,arikpoz/mxnet,piiswrong/mxnet,kkk669/mxnet,ZihengJiang/mxnet,dmlc/mxnet,ptrendx/mxnet,Ldpe2G/mxnet,lxn2/mxnet,lxn2/mxnet,larroy/mxnet,Ldpe2G/mxnet,piiswrong/mxnet,sxjscience/mxnet,Prasad9/incubator-mxnet,formath/mxnet,zhreshold/mxnet,eric-haibin-lin/mxnet,crazy-cat/incubator-mxnet,arank/mxnet,szha/mxnet,nicklhy/mxnet,antoan2/incubator-mxnet,gautamkmr/incubator-mxnet,reminisce/mxnet,indhub/mxnet,crazy-cat/incubator-mxnet,luoyetx/mxnet,Mega-DatA-Lab/mxnet,yuruofeifei/mxnet,xcgoner/dist-mxnet,likelyzhao/mxnet,Ldpe2G/mxnet,smolix/incubator-mxnet,yuruofeifei/mxnet,navrasio/mxnet,ykim362/mxnet,hesseltuinhof/mxnet,jamesliu/mxnet,lxn2/mxnet,pluskid/mxnet,antoan2/incubator-mxnet,smolix/incubator-mxnet,crazy-cat/incubator-mxnet,tlby/mxnet,stefanhenneking/mxnet,stefanhenneking/mxnet,Mega-DatA-Lab/mxnet,precedenceguo/mxnet,pluskid/mxnet,mbaijal/incubator-mxnet,piiswrong/mxnet,gautamkmr/incubator-mxnet,CodingCat/mxnet,kkk669/mxnet,LinkHS/incubator-mxnet,jermainewang/mxnet,tlby/mxnet,vikingMei/mxnet,larroy/mxnet,hpi-xnor/BMXNet,saurabh3949/mxnet,eric-haibin-lin/mxnet,gautamkmr/incubator-mxnet,ykim362/mxnet,jiajiechen/mxnet,ZihengJiang/mxnet,kkk669/mxnet,precedenceguo/mxnet,leezu/mxnet,DR08/mxnet,DickJC123/mxnet,sxjscience/mxnet,jiajiechen/mxnet,lxn2/mxnet,rahul003/mxnet,larroy/mxnet,jennyzhang0215/incubator-mxnet,arank/mxnet,precedenceguo/mxnet,CodingCat/mxnet,xcgoner/dist-mxnet,reminisce/mxnet,CodingCat/mxnet,zhreshold/mxnet,madjam/mxnet,Northrend/mxnet,apaleyes/mxnet,hpi-xnor/BMXNet,yuruofeifei/mxnet,solin319/incubator-mxnet,likelyzhao/mxnet,yajiedesign/mxnet,luoyetx/mxnet,apaleyes/mxnet,tornadomeet/mxnet,eric-haibin-lin/mxnet,ptrendx/mxnet,stefanhenneking/mxnet,kevinthesun/mxnet,likelyzhao/mxnet,DR08/mxnet,kkk669/mxnet,tornadomeet/mxnet,jennyzhang0215/incubator-mxnet,wangyum/mxnet,rahul003/mxnet,weleen/mxnet,yajiedesign/mxnet,ptrendx/mxnet,ShownX/incubator-mxnet,zhreshold/mxnet,wangyum/mxnet,precedenceguo/mxnet,nicklhy/mxnet,piiswrong/mxnet,jennyzhang0215/incubator-mxnet,Prasad9/incubator-mxnet,arank/mxnet,indhub/mxnet,ykim362/mxnet,lxn2/mxnet,danithaca/mxnet,crazy-cat/incubator-mxnet,indhub/mxnet,eric-haibin-lin/mxnet,fullfanta/mxnet,Northrend/mxnet,hesseltuinhof/mxnet,indhub/mxnet,hesseltuinhof/mxnet,hesseltuinhof/mxnet,reminisce/mxnet,dmlc/mxnet,TuSimple/mxnet,crazy-cat/incubator-mxnet,zhreshold/mxnet,arikpoz/mxnet,mbaijal/incubator-mxnet,reminisce/mxnet,larroy/mxnet,TuSimple/mxnet,madjam/mxnet,rishita/mxnet,rishita/mxnet,ZihengJiang/mxnet,luoyetx/mxnet,danithaca/mxnet,formath/mxnet,stefanhenneking/mxnet,sergeykolychev/mxnet,jermainewang/mxnet,Prasad9/incubator-mxnet,crazy-cat/incubator-mxnet,Ldpe2G/mxnet,jermainewang/mxnet,likelyzhao/mxnet,apache/incubator-mxnet,Prasad9/incubator-mxnet,mbaijal/incubator-mxnet,kkk669/mxnet,yajiedesign/mxnet,weleen/mxnet,arikpoz/mxnet,Mega-DatA-Lab/mxnet,ZihengJiang/mxnet,ForkedReposBak/mxnet,jermainewang/mxnet,vikingMei/mxnet,arikpoz/mxnet,yajiedesign/mxnet,fullfanta/mxnet,madjam/mxnet,CodingCat/mxnet,reminisce/mxnet,ShownX/incubator-mxnet,arikpoz/mxnet,luoyetx/mxnet,coder-james/mxnet,jamesliu/mxnet,szha/mxnet,TuSimple/mxnet,coder-james/mxnet,luoyetx/mxnet,sergeykolychev/mxnet,apache/incubator-mxnet,wangyum/mxnet,tlby/mxnet,madjam/mxnet,luoyetx/mxnet,ForkedReposBak/mxnet,pluskid/mxnet,apaleyes/mxnet,kevinthesun/mxnet,weleen/mxnet,dmlc/mxnet,sergeykolychev/mxnet,luoyetx/mxnet,hesseltuinhof/mxnet,Ldpe2G/mxnet,madjam/mxnet,navrasio/mxnet,jamesliu/mxnet,antoan2/incubator-mxnet,jermainewang/mxnet,ykim362/mxnet,pluskid/mxnet,hotpxl/mxnet,smolix/incubator-mxnet,smolix/incubator-mxnet,piiswrong/mxnet,sxjscience/mxnet,CodingCat/mxnet,solin319/incubator-mxnet,apache/incubator-mxnet,apaleyes/mxnet,navrasio/mxnet,tlby/mxnet,wangyum/mxnet,indhub/mxnet,gautamkmr/incubator-mxnet,EvanzzzZ/mxnet,hotpxl/mxnet,Mega-DatA-Lab/mxnet,ForkedReposBak/mxnet,yajiedesign/mxnet,antoan2/incubator-mxnet,TuSimple/mxnet,formath/mxnet,fullfanta/mxnet,rishita/mxnet,DR08/mxnet,weleen/mxnet,thirdwing/mxnet,mbaijal/incubator-mxnet,ptrendx/mxnet,madjam/mxnet,Northrend/mxnet,rahul003/mxnet,hpi-xnor/BMXNet,weleen/mxnet,leezu/mxnet,smolix/incubator-mxnet,crazy-cat/incubator-mxnet,DickJC123/mxnet,solin319/incubator-mxnet,tornadomeet/mxnet,madjam/mxnet,stefanhenneking/mxnet,EvanzzzZ/mxnet,rishita/mxnet,jamesliu/mxnet,xcgoner/dist-mxnet,ptrendx/mxnet,piiswrong/mxnet,formath/mxnet,xcgoner/dist-mxnet,hotpxl/mxnet,rishita/mxnet,smolix/incubator-mxnet,xcgoner/dist-mxnet,lxn2/mxnet,eric-haibin-lin/mxnet,DR08/mxnet,pluskid/mxnet,wangyum/mxnet,saurabh3949/mxnet,yuruofeifei/mxnet,arank/mxnet,likelyzhao/mxnet,indhub/mxnet,szha/mxnet,leezu/mxnet,coder-james/mxnet,hesseltuinhof/mxnet,ShownX/incubator-mxnet,kkk669/mxnet,reminisce/mxnet,EvanzzzZ/mxnet,precedenceguo/mxnet,ykim362/mxnet,zhreshold/mxnet,yuruofeifei/mxnet,lxn2/mxnet,leezu/mxnet,ZihengJiang/mxnet,ZihengJiang/mxnet,weleen/mxnet,jamesliu/mxnet,tlby/mxnet,thirdwing/mxnet,thirdwing/mxnet