Fix injecting empty CSS

Fix for bad requests being made when there's no CSS to be injected

Fix error message

v1.0.3

Fix request error message

Interactive tests support

Merge pull request #7 from Schibsted-Tech-Polska/interactive-tests

Interactive tests

ES6 refactor

Merge pull request #6 from Schibsted-Tech-Polska/es6-refactor

Es6 refactor

PhantomJS-based library

v1.0

fix error handler