ATMO-302 Fix account-management endpoint.

* Update username route to be less strict.
* Fix import statements so api/accounts.py actually works.

	modified:   api/accounts.py
	modified:   atmosphere/urls.py
ATMO-302 Fix account-management endpoint.

* Update username route to be less strict.
* Fix import statements so api/accounts.py actually works.

	modified:   api/accounts.py
	modified:   atmosphere/urls.py
Merge branch 'atmo-302'