Improve language stats for .net projects

This excludes some common js used in many .net project so that they
don't show up in language stats. Things exlude now include:
 - Visual Studio intellisense js files
 - Microsoft's Ajax and Validation js
 - Anything in the NuGet packages directory

lib/linguist/vendor.yml

@@ -73,3 +73,14 @@
 
 # Sparkle
 - (^|/)Sparkle/
+
+## .NET ##
+
+# Visual Studio IntelliSense
+- -vsdoc\.js$
+
+# Microsoft Ajax
+- (^|/)[Mm]icrosoft([Mm]vc)?([Aa]jax|[Vv]alidation)(\.debug)?\.js$
+
+# NuGet
+- ^[Pp]ackages/