Ignore .packages folder

I ran the CI build locally to test something and it generated loads of NuGet packages in the ".package" folder, so let's ignore that.

Author: martincostello

.gitignore

@@ -111,7 +111,7 @@ publish/
 *.Publish.xml
 
 # NuGet Packages Directory
-## TODO: If you have NuGet Package Restore enabled, uncomment the next line
+.packages/
 packages/
 
 # Windows Azure Build Output