Updated accordion.js to use ng-class

Updated accordion.js to use ng-class
renamed click_on_accordion_tab() ( fixed the misspelling )
Correct spelling in rating module.
Fix references to rating module in Gruntfile and README
Merge pull request #4 from studiothree10/master

Updated accordion.js to use ng-class
Merge pull request #5 from cgroner/spelling-rating

Correct spelling in rating module.
Update Contributors.md