feature(client): Error and tooltip fixes!

* Hide errors on form change if form is valid. Help with issue #765 where "Incorrect password" error is shown even after the user updates the password.
* Prevent form re-submission while form is disabled.
* Allow tooltips to be displayed when clicking "next" button even if form is disabled.

fixes #765
fixes #858
Merge pull request #839 from mozilla/issue-765-remove-error

feature(client): Error and tooltip fixes!
feature(client): Create two types of rendering, synchronous and asynchronous.

* Asynchronous can be used to check for prerequisites/errors before printing the template. Async is opt in.
refactor(client): Start to convert remaining views to use async rendering.

* Update tests.
* Update complete_sign_up to print invalid link error if the server says that the code/uid are invalid.
refactor(client): All views are converted to use asyncRender.
refactor(client): *all* rendering is async now. Remove 'renderer' declarations.