closes#6018
- added keyForAttribute method in application serializer
- override keyForAttribute in settings serializer to not apply camelCase/underscore conversion
- rename under_scored properties to camelCased
no issue
- updates ember-data dependency and switches to direct es6 module import instead of destructuring assignment
- fixes issue with `authenticationFailed` action being called before transitions have finished
no issue
- add ember-suave dependency
- upgrade grunt-jscs dependency
- add a new .jscsrc for the client's tests directory that extends from client's base .jscsrc
- separate client tests in Gruntfile jscs task so they pick up the test's .jscsrc
- standardize es6 usage across client