Remove automattic backend
Remove mollom backend
Remove typepad backend
Remove dependencies for third party spam checkers
Now cover the zinnia.spam_checkers.backends module
Update links for Akismet et Mollom spam checker backends
Remove references to Akismet, Typepad and Mollom spam checkers
Update ecosystem with zinnia-spam-checker-akismet and zinnia-spam-checker-mollom
Remove old reference
Merge branch 'feature/remove-third-party-spam-checkers' into develop