Fixed some issues with navigation below 768px

Applied some backgrounds to the navigation dropdown for screens smaller
than 768px.
Merge branch 'hotfix/nav-fix' of git://github.com/doot0/zf-web into hotfix/83
Compiled CSS via sass

- Also added Bourbon library (was required in app.css)
Added README about compiling CSS via SASS
Merge branch 'hotfix/83'

Close #83