Update appveyor.yml.
Update appveyor.yml.

Thanks @FeodorFitsner!

tazminweb/grunt-uncss,zabefloyd/grunt-uncss,sparanoid/grunt-uncss-inline,kingsj/grunt-uncss,tazminweb/grunt-uncss,addyosmani/grunt-uncss,simohaitham/grunt-uncss,addyosmani/grunt-uncss,sparanoid/grunt-uncss-inline,kingsj/grunt-uncss,zabefloyd/grunt-uncss,simohaitham/grunt-uncss