Adds login limiter

Closes #499
* On wrong passwords, statuses: `active` -> `warn-1` -> `warn-2` -> `warn-3` -> `locked`
* On login check, if user's status is `locked`, login automatically fails and user is encouraged to reset password. Does not even bother to check for passwords.
* login attempts tell user how many attempts she has remaining in notification box
* successful login will reset status to `active`
* resetting password with forgotten password emailed token resets status to `active`
* complete with a test suite