Merge branch 'release/3.0.3' into develop

* release/3.0.3:
  Bump to 3.0.3.
Run tests with Django 1.5
Update fields.py

Don't overwrite existing image when form saved
Added global boolean to prevent autodiscover() from being called more than once.
Discover image generators during lookup

Fixes GH-241
Merge branch 'nex2hex/develop' into develop

* nex2hex/develop:
  Update fields.py
Update IMAGEKIT_DEFAULT_FILE_STORAGE description
Add __getstate__ method to ImageCacheFile
Merge pull request #255 from nex2hex/develop

Add __getstate__ method to ImageCacheFile
Bump the version to 3.0.4.
Merge branch 'release/3.0.4'

* release/3.0.4:
  Bump the version to 3.0.4.
  Add __getstate__ method to ImageCacheFile
  Update IMAGEKIT_DEFAULT_FILE_STORAGE description
  Discover image generators during lookup
  Added global boolean to prevent autodiscover() from being called more than once.
  Update fields.py
  Run tests with Django 1.5