SPARK-1873: Add README.md file when making distributions
SPARK-1873: Add README.md file when making distributions

Author: Patrick Wendell <pwendell@gmail.com>

Closes #818 from pwendell/reamde and squashes the following commits:

4020b11 [Patrick Wendell] SPARK-1873: Add README.md file when making distributions

ConeyLiu/spark,janewangfb/spark,rikima/spark,setjet/spark,kiszk/spark,ahnqirage/spark,michalsenkyr/spark,rekhajoshm/spark,markhamstra/spark,alunarbeach/spark,sachintyagi22/spark,mdespriee/spark,esi-mineset/spark,andrewor14/spark,nlalevee/spark,wzhfy/spark,UndeadBaneGitHub/spark,kissmetrics/spark,LantaoJin/spark,apache-spark-on-k8s/spark,ibm-research-ireland/sparkoscope,jianran/spark,lxsmnv/spark,janewangfb/spark,taroplus/spark,ptkool/spark,akopich/spark,mzl9039/spark,zero323/spark,poffuomo/spark,skonto/spark,ron8hu/spark,byakuinss/spark,bdrillard/spark,ajaysaini725/spark,akopich/spark,jiangxb1987/spark,jkbradley/spark,pgandhi999/spark,eyalfa/spark,yanboliang/spark,WindCanDie/spark,MLnick/spark,huang1900/spark,JoshRosen/spark,markhamstra/spark,taroplus/spark,ueshin/apache-spark,spark-test/spark,bdrillard/spark,dhruve/spark,icexelloss/spark,shuangshuangwang/spark,JerryLead/spark,aosagie/spark,HyukjinKwon/spark,actuaryzhang/spark,big-pegasus/spark,gengliangwang/spark,WindCanDie/spark,caneGuy/spark,szhem/spark,zhouyejoe/spark,wangmiao1981/spark,mahak/spark,mdespriee/spark,skonto/spark,pronix/spark,witgo/spark,liutang123/spark,kiszk/spark,taroplus/spark,zhouyejoe/spark,yanboliang/spark,markhamstra/spark,andrewor14/spark,patrick-nicholson/spark,actuaryzhang/spark,apache/spark,hhbyyh/spark,nilsgrabbert/spark,rezasafi/spark,publicRoman/spark,gengliangwang/spark,actuaryzhang/spark,jrshust/spark,WindCanDie/spark,szhem/spark,saturday-shi/spark,cin/spark,ptkool/spark,dongjoon-hyun/spark,saltstar/spark,jiangxb1987/spark,liyichao/spark,wangmiao1981/spark,joseph-torres/spark,patrick-nicholson/spark,highfei2011/spark,gioenn/xSpark,jlopezmalla/spark,narahari92/spark,liyichao/spark,brad-kaiser/spark,milliman/spark,liutang123/spark,srowen/spark,hvanhovell/spark,1haodian/spark,byakuinss/spark,jkbradley/spark,maropu/spark,aray/spark,kevinyu98/spark,ron8hu/spark,mike0sv/spark,kiszk/spark,saltstar/spark,mdespriee/spark,icexelloss/spark,hvanhovell/spark,metamx/spark,WeichenXu123/spark,lvdongr/spark,cin/spark,jiangxb1987/spark,rednaxelafx/apache-spark,skonto/spark,bOOm-X/spark,ddna1021/spark,alunarbeach/spark,1haodian/spark,1haodian/spark,JoshRosen/spark,SHASHANKB/spark,xflin/spark,wangmiao1981/spark,rikima/spark,SnappyDataInc/spark,map222/spark,cloud-fan/spark,janewangfb/spark,zhouyejoe/spark,gioenn/xSpark,byakuinss/spark,gioenn/xSpark,shubhamchopra/spark,mahak/spark,tengpeng/spark,publicRoman/spark,BryanCutler/spark,big-pegasus/spark,panfengfeng/spark,zero323/spark,cin/spark,mdespriee/spark,WeichenXu123/spark,nlalevee/spark,lxsmnv/spark,xuanyuanking/spark,stanzhai/spark,narahari92/spark,lxsmnv/spark,kevinyu98/spark,metamx/spark,1haodian/spark,dongjoon-hyun/spark,dhruve/spark,darionyaphet/spark,cin/spark,LantaoJin/spark,BryanCutler/spark,nchammas/spark,panfengfeng/spark,brad-kaiser/spark,stanzhai/spark,saturday-shi/spark,zzcclp/spark,darionyaphet/spark,mike0sv/spark,szhem/spark,aokolnychyi/spark,yanboliang/spark,jrshust/spark,tejasapatil/spark,aray/spark,zuotingbing/spark,chuckchen/spark,shubhamchopra/spark,setjet/spark,wangyum/spark,mzl9039/spark,debugger87/spark,Aegeaner/spark,actuaryzhang/spark,zuotingbing/spark,jianran/spark,jianran/spark,JoshRosen/spark,rekhajoshm/spark,Aegeaner/spark,haowu80s/spark,michalsenkyr/spark,nchammas/spark,esi-mineset/spark,someorz/spark,maropu/spark,hvanhovell/spark,rikima/spark,publicRoman/spark,patrick-nicholson/spark,szhem/spark,liutang123/spark,pgandhi999/spark,dhruve/spark,joseph-torres/spark,ahnqirage/spark,JerryLead/spark,poffuomo/spark,ptkool/spark,szhem/spark,adrian-ionescu/apache-spark,kevinyu98/spark,wangyum/spark,zhouyejoe/spark,Panos-Bletsos/spark-cost-model-optimizer,actuaryzhang/spark,adrian-ionescu/apache-spark,guoxiaolongzte/spark,joseph-torres/spark,wangyum/spark,kiszk/spark,ron8hu/spark,dongjoon-hyun/spark,guoxiaolongzte/spark,apache/spark,someorz/spark,SHASHANKB/spark,xflin/spark,icexelloss/spark,gengliangwang/spark,jrshust/spark,andrewor14/spark,dongjoon-hyun/spark,zero323/spark,xuanyuanking/spark,ConeyLiu/spark,SHASHANKB/spark,haowu80s/spark,dbtsai/spark,taroplus/spark,ron8hu/spark,rednaxelafx/apache-spark,ahnqirage/spark,WeichenXu123/spark,zero323/spark,someorz/spark,mzl9039/spark,loneknightpy/spark,techaddict/spark,joseph-torres/spark,metamx/spark,witgo/spark,nchammas/spark,byakuinss/spark,MLnick/spark,HyukjinKwon/spark,maropu/spark,ConeyLiu/spark,WindCanDie/spark,stanzhai/spark,michalsenkyr/spark,rikima/spark,zzcclp/spark,highfei2011/spark,witgo/spark,haowu80s/spark,huang1900/spark,pgandhi999/spark,poffuomo/spark,rikima/spark,akopich/spark,tengpeng/spark,sureshthalamati/spark,nilsgrabbert/spark,rikima/spark,lvdongr/spark,zzcclp/spark,andrewor14/iolap,panfengfeng/spark,andrewor14/spark,pgandhi999/spark,sureshthalamati/spark,mzl9039/spark,darionyaphet/spark,bOOm-X/spark,guoxiaolongzte/spark,ajaysaini725/spark,byakuinss/spark,ioana-delaney/spark,minixalpha/spark,jkbradley/spark,bravo-zhang/spark,taroplus/spark,minixalpha/spark,byakuinss/spark,ConeyLiu/spark,mzl9039/spark,lxsmn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,saltstar/spark,kissmetrics/spark,ConeyLiu/spark,facaiy/spark,narahari92/spark,nlalevee/spark,vinodkc/spark,lvdongr/spark,jianran/spark,loneknightpy/spark,SHASHANKB/spark,brad-kaiser/spark,goldmedal/spark,rezasafi/spark,holdenk/spark,eyalfa/spark,wzhfy/spark,narahari92/spark,tengpeng/spark,pronix/spark,techaddict/spark,sahilTakiar/spark,ueshin/apache-spark,patrick-nicholson/spark,matthewfranglen/spark,ptkool/spark,map222/spark,nilsgrabbert/spark,techaddict/spark,xflin/spark,rezasafi/spark,xuanyuanking/spark,ahnqirage/spark,taroplus/spark,facaiy/spark,narahari92/spark,SHASHANKB/spark,Aegeaner/spark,HyukjinKwon/spark,alunarbeach/spark,tejasapatil/spark,JerryLead/spark,WeichenXu123/spark,bdrillard/spark,WindCanDie/spark,rezasafi/spark,shuangshuangwang/spark,techaddict/spark,tengpeng/spark,rezasafi/spark,wangmiao1981/spark,saltstar/spark,zuotingbing/spark,ericvandenbergfb/spark,techaddict/spark,pgandhi999/spark,WindCanDie/spark,zero323/spark,ioana-delaney/spark,jiangxb1987/spark,BryanCutler/spark,ahnqirage/spark,rednaxelafx/apache-spark,zuotingbing/spark,ioana-delaney/spark,kimoonkim/spark,lvdongr/spark,apache/spark,srowen/spark,aokolnychyi/spark,esi-mineset/spark,stanzhai/spark,BryanCutler/spark,poffuomo/spark,gengliangwang/spark,ptkool/spark,loneknightpy/spark,shubhamchopra/spark,andrewor14/iolap,dongjoon-hyun/spark,shuangshuangwang/spark,panfengfeng/spark,darionyaphet/spark,cloud-fan/spark,lxsmnv/spark,pronix/spark,aokolnychyi/spark,nchammas/spark,eyalfa/spark,ddna1021/spark,HyukjinKwon/spark,jlopezmalla/spark,nilsgrabbert/spark,cin/spark,wangmiao1981/spark,hhbyyh/spark,SnappyDataInc/spark,bdrillard/spark,brad-kaiser/spark,esi-mineset/spark,SnappyDataInc/spark,markhamstra/spark,apache-spark-on-k8s/spark,aosagie/spark,kissmetrics/spark,wzhfy/spark,loneknightpy/spark,ddna1021/spark,ioana-delaney/spark,jianran/spark,metamx/spark,SnappyDataInc/spark,andrewor14/spark,facaiy/spark,nlalevee/spark,wzhfy/spark,liyichao/spark,cloud-fan/spark,HyukjinKwon/spark,vinodkc/spark,SHASHANKB/spark,vinodkc/spark,aosagie/spark,srowen/spark,JerryLead/spark,liutang123/spark,ibm-research-ireland/sparkoscope,setjet/spark,shubhamchopra/spark,ioana-delaney/spark,gioenn/xSpark,spark-test/spark,Panos-Bletsos/spark-cost-model-optimizer,spark-test/spark,lvdongr/spark,akopich/spark,andrewor14/iolap,andrewor14/iolap,nlalevee/spark,milliman/spark,witgo/spark,UndeadBaneGitHub/spark,aosagie/spark,goldmedal/spark,aosagie/spark,kimoonkim/spark,joseph-torres/spark,sahilTakiar/spark,andrewor14/spark,dongjoon-hyun/spark,loneknightpy/spark,liutang123/spark,mdespriee/spark,kevinyu98/spark,andrewor14/iolap,yanboliang/spark,michalsenkyr/spark,milliman/spark,guoxiaolongzte/spark,chuckchen/spark,saturday-shi/spark,caneGuy/spark,caneGuy/spark,narahari92/spark,kevinyu98/spark,vinodkc/spark,sachintyagi22/spark,jrshust/spark,wangyum/spark,michalsenkyr/spark,taroplus/spark,JoshRosen/spark,tengpeng/spark,UndeadBaneGitHub/spark,nilsgrabbert/spark,maropu/spark,goldmedal/spark,map222/spark,rekhajoshm/spark,janewangfb/spark,bOOm-X/spark,Panos-Bletsos/spark-cost-model-optimizer,big-pegasus/spark,metamx/spark,spark-test/spark,ueshin/apache-spark,ueshin/apache-spark,cloud-fan/spark,rednaxelafx/apache-spark,eyalfa/spark,big-pegasus/spark,ioana-delaney/spark,huang1900/spark,xflin/spark,wangyum/spark,minixalpha/spark,dhruve/spark,debugger87/spark,jkbradley/spark,lvdongr/spark,icexelloss/spark,publicRoman/spark,guoxiaolongzte/spark,shubhamchopra/spark,andrewor14/spark,debugger87/spark,michalsenkyr/spark,kimoonkim/spark,szhem/spark,tejasapatil/spark,srowen/spark,ibm-research-ireland/sparkoscope,Aegeaner/spark,minixalpha/spark,bdrillard/spark,pgandhi999/spark,ueshin/apache-spark,debugger87/spark,saltstar/spark,mzl9039/spark,nchammas/spark,Panos-Bletsos/spark-cost-model-optimizer,zuotingbing/spark,apache/spark,HyukjinKwon/spark,JerryLead/spark,publicRoman/spark,poffuomo/spark,eyalfa/spark,dhruve/spark,map222/spark,panfengfeng/spark,icexelloss/spark,ConeyLiu/spark,rezasafi/spark,sahilTakiar/spark,jkbradley/spark,huang1900/spark,xuanyuanking/spark,markhamstra/spark,publicRoman/spark,sachintyagi22/spark,spark-test/spark,bdrillard/spark,poffuomo/spark,nchammas/spark,facaiy/spark,ioana-delaney/spark,milliman/spark,rekhajoshm/spark,lvdongr/spark,sahilTakiar/spark,metamx/spark,poffuomo/spark,cloud-fan/spark,apache-spark-on-k8s/spark,ron8hu/spark,ddna1021/spark,skonto/spark,apache/spark,nlalevee/spark,panfengfeng/spark,highfei2011/spark,someorz/spark,ajaysaini725/spark,zuotingbing/spark,someorz/spark,UndeadBaneGitHub/spark,zero323/spark,eyalfa/spark,markhamstra/spark,publicRoman/spark,shuangshuangwang/spark,huang1900/spark,bravo-zhang/spark,patrick-nicholson/spark,pronix/spark,JoshRosen/spark,ericvandenbergfb/spark,MLnick/spark,highfei2011/spark,zero323/spark,mzl9039/spark,apache-spark-on-k8s/spark,WeichenXu123/spark,nilsgrabbert/spark,yanboliang/spark,mahak/spark,caneGuy/spark,tejasapatil/spark,holdenk/spark,dbtsai/spark,vinodkc/spark,Panos-Bletsos/spark-cost-model-optimizer,aray/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