support displayFeatures of GA, both ga.js and analytics.js
fix jshint warnings
fix test case: missing configuration before testing existence of gc.js
update README.md
update README.md
Merge branch 'support-display-features' of https://github.com/JimmyChange/angular-google-analytics into support-display-features
Merge pull request #40 from JimmyChange/support-display-features

support displayFeatures of GA, both ga.js and analytics.js