Change /* comments inside SCSS selectors to //

This type of commet can cause empty rules to be emitted
http://sass-lang.com/docs/yardoc/file.SASS_REFERENCE.html#comments
This classes should get removed by the compressor, but still get flagged
by CSSLint
Merge pull request #995 from nschonni/single-line-comments-in-nested-scss

Change /* comments inside SCSS selectors to //