Added a readme to explain the need for two different .csproj files.
Added a readme to explain the need for two different .csproj files.

Vedin/corefxlab,stephentoub/corefxlab,VSadov/corefxlab,ahsonkhan/corefxlab,stephentoub/corefxlab,tarekgh/corefxlab,stephentoub/corefxlab,mafiya69/corefxlab,ahsonkhan/corefxlab,joshfree/corefxlab,Vedin/corefxlab,benaadams/corefxlab,ravimeda/corefxlab,stephentoub/corefxlab,ericstj/corefxlab,alexperovich/corefxlab,ericstj/corefxlab,ericstj/corefxlab,whoisj/corefxlab,ericstj/corefxlab,VSadov/corefxlab,ericstj/corefxlab,joshfree/corefxlab,ericstj/corefxlab,stephentoub/corefxlab,Vedin/corefxlab,whoisj/corefxlab,Vedin/corefxlab,KrzysztofCwalina/corefxlab,stephentoub/corefxlab,adamsitnik/corefxlab,Vedin/corefxlab,dotnet/corefxlab,VSadov/corefxlab,VSadov/corefxlab,dotnet/corefxlab,KrzysztofCwalina/corefxlab,VSadov/corefxlab,tarekgh/corefxlab,livarcocc/corefxlab,Vedin/corefxlab,VSadov/corefxlab,hanblee/corefxlab,benaadams/corefxlab,adamsitnik/corefxlab,nguerrera/corefxlab,weshaggard/corefxlab,hanblee/corefxlab