Try updating npm to fix appveyor

Author: lukeapage

appveyor.yml

@@ -14,6 +14,10 @@ matrix:
 install:
   # Get the latest stable version of Node 0.STABLE.latest
   - ps: Install-Product node $env:nodejs_version
+  # Use npm v2
+  - npm -g install npm@2
+  - set PATH=%APPDATA%\npm;%PATH%
+  - npm -v
   # Typical npm stuff.
   - npm install
   # Grunt-specific stuff.