Adding create-on-demand, serialization & image warming

Serialization for Django REST Framework
First-pass at serialization/performance docs
Docs edits/clean-up
Updating README to match recent docs changes
More minor docs edits
Bumping to version 0.2 for PyPI release
Fixing minor syntax error in README
Minor docs editing/clean-up
Ensuring admin thumbnails are always available
Bumping to 0.2.1 in preparation for PyPI release
Moving requirements into a separate file
Scaffolding in testing architecture
Adding a tests-specific app

Includes:
* Models + fixture data
* Settings
* Media used in fixture
Adding first-pass at tests

Includes testing:
* Setting PPOI
* PPOI Validation
* Resized paths
* Filtered paths
* Caching integration
* create_on_demand setting and functionality
* image warming
Swapping out point-releases in travis config
Attempting to squash Travis error around settings.configure()
Attempting to squash Travis DJANGO_SETTINGS_MODULE unset error
Catching ImportError for django < 1.7
Setting 'upload_to' properly for django < 1.7
Updating runtest.py to be django < 1.7 compatible