Update versions in post-dev15 branch to 2.1.0-beta1 (take 2)
Update versions in post-dev15 branch to 2.1.0-beta1 (take 2)

lorcanmooney/roslyn,abock/roslyn,abock/roslyn,ErikSchierboom/roslyn,stephentoub/roslyn,paulvanbrenk/roslyn,bkoelman/roslyn,swaroop-sridhar/roslyn,zooba/roslyn,gafter/roslyn,srivatsn/roslyn,mavasani/roslyn,akrisiun/roslyn,Giftednewt/roslyn,bartdesmet/roslyn,jcouv/roslyn,khyperia/roslyn,mmitche/roslyn,mattscheffer/roslyn,CyrusNajmabadi/roslyn,weltkante/roslyn,dotnet/roslyn,cston/roslyn,khyperia/roslyn,nguerrera/roslyn,swaroop-sridhar/roslyn,drognanar/roslyn,cston/roslyn,drognanar/roslyn,agocke/roslyn,mattwar/roslyn,mmitche/roslyn,Hosch250/roslyn,jmarolf/roslyn,ErikSchierboom/roslyn,genlu/roslyn,bkoelman/roslyn,bkoelman/roslyn,shyamnamboodiripad/roslyn,tvand7093/roslyn,aelij/roslyn,tmeschter/roslyn,jkotas/roslyn,paulvanbrenk/roslyn,tmat/roslyn,robinsedlaczek/roslyn,jkotas/roslyn,aelij/roslyn,lorcanmooney/roslyn,shyamnamboodiripad/roslyn,pdelvo/roslyn,AlekseyTs/roslyn,brettfo/roslyn,TyOverby/roslyn,jcouv/roslyn,wvdd007/roslyn,diryboy/roslyn,jasonmalinowski/roslyn,MichalStrehovsky/roslyn,tmat/roslyn,yeaicc/roslyn,brettfo/roslyn,jasonmalinowski/roslyn,mgoertz-msft/roslyn,TyOverby/roslyn,mattscheffer/roslyn,KirillOsenkov/roslyn,weltkante/roslyn,zooba/roslyn,cston/roslyn,AdamSpeight2008/roslyn-AdamSpeight2008,eriawan/roslyn,Hosch250/roslyn,gafter/roslyn,AlekseyTs/roslyn,ErikSchierboom/roslyn,DustinCampbell/roslyn,srivatsn/roslyn,jamesqo/roslyn,diryboy/roslyn,yeaicc/roslyn,davkean/roslyn,VSadov/roslyn,heejaechang/roslyn,CaptainHayashi/roslyn,khyperia/roslyn,zooba/roslyn,AmadeusW/roslyn,AmadeusW/roslyn,genlu/roslyn,physhi/roslyn,DustinCampbell/roslyn,diryboy/roslyn,jeffanders/roslyn,agocke/roslyn,MattWindsor91/roslyn,mattscheffer/roslyn,dotnet/roslyn,dpoeschl/roslyn,KirillOsenkov/roslyn,OmarTawfik/roslyn,heejaechang/roslyn,yeaicc/roslyn,MattWindsor91/roslyn,wvdd007/roslyn,tmeschter/roslyn,tannergooding/roslyn,AmadeusW/roslyn,amcasey/roslyn,AlekseyTs/roslyn,davkean/roslyn,agocke/roslyn,wvdd007/roslyn,shyamnamboodiripad/roslyn,amcasey/roslyn,mavasani/roslyn,jamesqo/roslyn,akrisiun/roslyn,kelltrick/roslyn,AnthonyDGreen/roslyn,abock/roslyn,kelltrick/roslyn,OmarTawfik/roslyn,orthoxerox/roslyn,nguerrera/roslyn,swaroop-sridhar/roslyn,sharwell/roslyn,tvand7093/roslyn,CaptainHayashi/roslyn,KevinRansom/roslyn,reaction1989/roslyn,eriawan/roslyn,brettfo/roslyn,genlu/roslyn,dotnet/roslyn,KevinRansom/roslyn,bartdesmet/roslyn,jcouv/roslyn,mattwar/roslyn,paulvanbrenk/roslyn,pdelvo/roslyn,gafter/roslyn,xasx/roslyn,mavasani/roslyn,eriawan/roslyn,panopticoncentral/roslyn,AdamSpeight2008/roslyn-AdamSpeight2008,robinsedlaczek/roslyn,bartdesmet/roslyn,AnthonyDGreen/roslyn,tvand7093/roslyn,OmarTawfik/roslyn,xasx/roslyn,tmat/roslyn,davkean/roslyn,Hosch250/roslyn,CaptainHayashi/roslyn,drognanar/roslyn,lorcanmooney/roslyn,jeffanders/roslyn,heejaechang/roslyn,VSadov/roslyn,MattWindsor91/roslyn,MattWindsor91/roslyn,reaction1989/roslyn,physhi/roslyn,VSadov/roslyn,mmitche/roslyn,DustinCampbell/roslyn,TyOverby/roslyn,physhi/roslyn,orthoxerox/roslyn,amcasey/roslyn,srivatsn/roslyn,stephentoub/roslyn,panopticoncentral/roslyn,sharwell/roslyn,Giftednewt/roslyn,CyrusNajmabadi/roslyn,dpoeschl/roslyn,nguerrera/roslyn,jmarolf/roslyn,dpoeschl/roslyn,pdelvo/roslyn,aelij/roslyn,xasx/roslyn,tannergooding/roslyn,jamesqo/roslyn,sharwell/roslyn,mgoertz-msft/roslyn,akrisiun/roslyn,tmeschter/roslyn,tannergooding/roslyn,KirillOsenkov/roslyn,MichalStrehovsky/roslyn,KevinRansom/roslyn,Giftednewt/roslyn,CyrusNajmabadi/roslyn,MichalStrehovsky/roslyn,AnthonyDGreen/roslyn,mgoertz-msft/roslyn,jmarolf/roslyn,jasonmalinowski/roslyn,weltkante/roslyn,kelltrick/roslyn,AdamSpeight2008/roslyn-AdamSpeight2008,jkotas/roslyn,stephentoub/roslyn,mattwar/roslyn,robinsedlaczek/roslyn,orthoxerox/roslyn,reaction1989/roslyn,panopticoncentral/roslyn,jeffanders/roslyn