Add Django 1.7 to supported versions, update tox.ini and .travis.yml.
SortedDict is deprecated, switch to OrderedDict API usage.
Validation error must not have an error_dict when raised within clean_<field>

We are raising a ValidationError inside clean_token, so setting the
error field to 'token' is redundant.
Avoid hitting multiple redirect in admin site.

Admin in 1.7 features a proper redirect to login
handling introduced in django/django@be0ad62994a340ad54a0b328771931932a45a899
Model equality check has changed for models without pk.

Introduced in django/django@6af05e7a0f0e4604d6a67899acaa99d73ec0dfaa
Checking models for equality will use id() if they do not have
a primary key yet, i.e. haven't been persisted yet.
We overwrite PhoneDevice.__eq__ to make sure we have the same
instances where needed.
Merge pull request #41 from julianwachholz/django17
Test 1.7 compatibility against supported Python versions