Ignore files generated by NuGet v3 project.json

Author: AArnott

VisualStudio.gitignore

@@ -151,6 +151,9 @@ publish/
 !**/packages/build/
 # Uncomment if necessary however generally it will be regenerated when needed
 #!**/packages/repositories.config
+# NuGet v3's project.json files produces more ignoreable files
+*.nuget.props
+*.nuget.targets
 
 # Windows Azure Build Output
 csx/