add Adamax & Nadam (#6784)
add Adamax & Nadam (#6784)

* add Adamax & Nadam

* change abs to NDabs

* update nadam

* Update optimizer.py

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