Initial port from djangosnippets repo.

This includes many fixes for Django > 1.4 compatibility, renames
a model field (django_version to version) and updates the search
index to use the Haystack 2.x API.
Added Travis config.
added 404 test template
Added Travis image.
Added link to Travis page
Comment out Django 1.6 for now since the tests are broken due to django-simple-ratings not working there.
Downgrade django-registration for now.
Use akismet spam fighter for comments.
Added django-recaptcha as a dependency.
Enable keyword check.
Use django-registration 1.0 and django-simple-captcha.
Use raw_id_fields for users and snippets.
Merge pull request #2 from zerok/feature/raw_id_fields

Use raw_id_fields for users and snippets.
Add CAB_VERSIONS to test settings as fixture.
Allow users to remove their own votes.
Use newer django-simple-ratings to fix backward compat issue with hashlib.
Use url tag for reset-rating link.
Merge pull request #6 from zerok/feature/unrate

Allow users to remove their own votes.
Update .travis.yml according to userguide.
Remove no-longer used test requirement