chore(ignore): ignore coverage directory
chore(jshint): add some globals
chore(dependencies): update to angular 1.2.23
chore(build): remove unnecessary variables from gulpfile
chore(build): add coverage reports to karma setup and update jasmine
style(module): remove unnecessary promise rejection cases

`loadDeferred` is never rejected so I removed all cases where
a possible error should be thrown in this case like 'Facebook API
could not be initialized properly'.

Also the subscribe and unsubscribe methods were merged by a forEach.
test(provider): add another test for init method
test(service): add tests for the service

new coverage for angular-facebook.js 97.19% :ghost: