refactor auth backends

add Id Site backend
add id site views and urls mappings
add id site example to test project
add id site info to the readme
rename stormpath_django to django_stormpath

As discussed with Randall we will be consistent with the django
ecosystem and it's naming, although the repo will remain stormpath-django
to be consistent with stormpaths naming.
Merge pull request #12 from denibertovic/develop

Django ID Site itegration