project management - use new-style, standard tags for easy deprecation feature searching
Fix response caching key names and make the key names all around better.

- resolves armstrong/armstrong#100, which was noticed because we used the Backend name in the key and it broke with a space in the name
- now use the Backend pk and slugify the URL, which is safer anyway
- add tests to confirm the cache is set properly and deleted on save
test juggling for EmbedAdmin

- the creation test should only happen in the AddTestCase
- the shared test class shouldn't have the "add" url
- there shouldn't *be* an "add" url, just a url which depends on the AddTestCase or ChangeTestCase
testing - arbitrary change in YouTube response data

(the image url is "i.ytimg.com" not "i1.ytimg.com"; url uses https)
minor non-functional change - don't need `formtools` in INSTALLED_APPS

(pretty sure this is because we aren't using their templates)
update to use atomic() introduced with the new transaction system in Django 1.6

This removes a PendingDeprecationWarning.
tests Django 1.7 - remove app loading warning

"RemovedInDjango19Warning: Model class tests.support.models.TypeModel doesn't declare an explicit app_label and either isn't in an application in INSTALLED_APPS or else was imported before its application was loaded."
testing - fix "RemovedInDjango19Warning: django.utils.unittest will be removed in Django 1.9" and Tox/TravisCI are already installing unittest2 in PY26
easiest way to remove "PendingDeprecationWarning: Options.module_name has been deprecated in favor of model_name" in Django 1.6
migrations - use South 1.0 and `south_migrations/` in prep for Django 1.7
migrations - add Django 1.7
explicitly declare MIDDLEWARE_CLASSES because the defaults change in Django 1.7
be explicit about GET and POST. Fixes RemovedInDjango19Warning about MergeDict and request.REQUEST
Fix "RemovedInDjango19Warning: The django.contrib.admin.util module has been renamed"
tests - Django 1.7 uses a more traditional 302 redirect to the login page

Alternatively could have added `follow=True` to the client.get() which works for all Django versions. This is more explicit though.
changes, readme and metadata update