chore(travis): run protractor tests with ff28

FirefoxDriver seems to have an issue with FF29 which is breaking a test case, and causing false negatives.

There is an issue opened on protractor regarding this at https://github.com/angular/protractor/issues/784

Closes #7369
feat($interpolate): add support for bind-once and lazy bind-once

With this optimization, it's now possible for $interpolated expressions to cease evaluating expressions
when it determines them to be finalized, and $watch will now unwatch finalized interpolated expressions.