Remove .sass-cache folder from gitignore

Using LibSass instead of Ruby Sass removed the `.sass-cache` folder.
Merge pull request #559 from antleblanc/master

Remove .sass-cache folder from gitignore
Don't install sass

5b860b29 removed the dependency on sass.
Merge pull request #567 from ithinkihaveacat/patch-1

Don't install sass
Fixes #570 - osx font smoothing for mox
fetch upstream google [modified gitignore & travis.yml] & add untracked global.scss