docs($http): clarify documentation on error status codes

Modify the documentation for $http to correspond to what Angular
considers a success status code.

Closes #1693
docs(form): minor form doc and example fixes

Form documentation fixes:
- Fix broken form example in docs
- A few small other corrections in form docs.
docs(faq): add info on logo reuse and how to get t-shirts and stickers
docs(forms): fix code example for a custom form control

Closes #1021
docs(guide): fix typos in unit test guide