remove Roslyn cache directory for VS 2015 CTP 1-4

VisualStudio.gitignore

@@ -22,9 +22,6 @@ bld/
 [Bb]in/
 [Oo]bj/
 
-# Roslyn cache directories
-*.ide/
-
 # Visual Studo 2015 cache/options directory
 .vs/