Remove spec/dummy/db/schema.rb from version control
Remove thredded_posts.user_email column

* No effect on performance (users are already preloaded).
* No special handling required when a user changes their email.
Avatar enhancements

* New option `avatar_url` to allow for custom avatar handling,
  `avatar_default` removed.
* Extract duplicate code to BaseUserTopicDecorator.
* Do not render avatar for anonymous users.
Merge pull request #41 from glebm/avatars

Avatars Refactoring