Allow use of @import statements in CSS.

* A flag has been added to project.json "inline_imports" which
allows you to specify whether or not you would like @imports
to be included inline in that CSS file or treated as they
normally are in CSS.
Adds circle.yml
Adds tests
Bump Version
Merge pull request #60 from mobify/inline-css-imports

Allow use of @import statements in CSS.