VisualStudio: Include the packages/repositories.config file.

I agree to ignore the NuGet packages folder, but I really think you should check in the repositories.config so NuGet PackageRestore can do it's magic when someone pulls the code and tries to build it...

VisualStudio.gitignore

@@ -89,6 +89,7 @@ publish/
 # NuGet Packages Directory
 ## TODO: If you have NuGet Package Restore enabled, uncomment the next line
 #packages/
+!packages/repositories.config
 
 # Windows Azure Build Output
 csx