docs(ngMock): grammar fix

Small grammar fix for mock $httpBackend documentation.
docs(form.FormController): fix grammar
fix(input): don't dirty model when input event triggered due to placeholder change

Certain versions of IE inexplicably trigger an input event in response to a placeholder
being set.

It is not possible to sniff for this behaviour nicely as the event is not triggered if
the element is not attached to the document, and the event triggers asynchronously so
it is not possible to accomplish this without deferring DOM compilation and slowing down
load times.

Closes #2614
Closes #5960
style(input): fix trailing whitespace

Oops. I blame vim for this little accident.
docs(tutorial/step_12): fix grammar
chore(Scope): name the $watch deregistration function as
chore(jshint): add jshint for the test/ folder