Needs some cleanup, but this has one form where user can change username and password (they can leave either the same if they just want to change one, but we should make this clearer.)
Add hint that password change is optional
Slight refactoring of partials
Admins cannot update a user. Eventually we will want to allow admins to update some user fields.
Merge pull request #28 from leapcode/feature/change_login

Feature/change login