Done using isort[1], with the following command:
```
isort -rc ./app ./tests
```
Adds linting to the `run_tests.sh` script to stop badly-sorted imports
getting re-introduced.
Chosen style is ‘Vertical Hanging Indent’ with trailing commas, because
I think it gives the cleanest diffs, eg:
```
from third_party import (
lib1,
lib2,
lib3,
lib4,
)
```
1. https://pypi.python.org/pypi/isort
This PR changes the flow to change an email address.
Once the user enter their password, they are told "Check your email".
An email has been sent to them containing a link to notify which contains an encrypted token.
The encrypted token contains the user id and new email address. Once the link is clicked the user's email address is updated to the new email address.
They are redirected to the /user-profile page.
Also in this commit is an update from flask.ext.login to flask_login.
NOTE: you can not test that the session is cleared out by checking the session cookie does not exist on the index page,
because ItsDangerousSession will create a new session when it hits the index page. The unit test confirms that the session has been cleared.
