Django-bakery

- Changed `AutoPublishingBuildableModel` to commit to the database before triggering a task
- Changed Celery tasks to accept primary keys instead of model objects

- An `AutoPublishingBuildableModel` that is able to use a Celery job queue to automatically build and publish objects when they are saved
- Refactored `build` management command to allow for its different tasks to be more easily overridden
- Added a `--keep-build-dir` option to the `build` command.

- Refactored the `publish` and `unpublish` management commands to use boto instead of s3cmd.
- `build` and `publish` management commands use file mimetypes instead of a regex on the filename to decide if a file will be gzipped.
- `publish` management command includes --force and --dry-run uploads to force an upload of all file, regardless of changes, and to print output without uploading files, respectively.
- `publish` management command now pools uploads to increase speed

- Added a `get_content` method to all of the buildable views to make it easier to build pages that don't require a template, like JSON outputs

- Bug fix with calculating Python version in the views in v0.4.0

- Added optional gzip support to build routine for Amazon S3 publishing (via [emamd](https://twitter.com/emamd))
- Mixin buildable view with common methods