Fix password reset functionality.

Add a feature spec that encompasses the whole flow, our other tests only cover
individual sections and weren't enough to catch this bug.
Don't test for the reset password token in the email.

It's not the point of this test, and its correct anymore. This functionality
is covered more broadly in the feature spec in the proceeding commit.
Merge pull request #243 from alphagov/fix-password-reset

Fix Password Reset