Djpubsubhubbub

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- Django 1.6 Compat. Pull Request 6
- Remove 200 character limit for URL field. Pull Request 5

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- Added support for callback scheme. Issue 5
- Added support for django.utils.timezone if available. Issue 6
- Adding basic support for GET calls and implementing status call. Pull Request 2
- Implementing retrieve call. Pull Request 3
- Fixed small coding issues that cause errors. Pull Request 4

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- Lots of stuff. No changelog was kept :(