Merge pull request #3 from udacity/development

Merge latest changes from upstream.
Merge pull request #6 from udacity/development

Merged with upstream and moved SSO sign-in to plugin
Merge pull request #8 from udacity/development

Merge latest changes from upstream.
Merge pull request #12 from udacity/development

Merged development into master for deployment
FIX: avatar thumbnail won't save after upload
Merge pull request #1391 from ZogStriP/fix-avatar-thumbnail-wont-save-after-upload

FIX: avatar thumbnail won't save after upload
Better API for adding on to our Dialect
annotate models
user simulator was bust
digest interfaces returning empty objects (except for id) interface needed correction
group the "suggested topics" by category correctly.

in the past new topics were not prioritizing current category and
new topics in a category were not being inserted before other unread topics
in other categories
invite only forums had very wonky logic, invited users were not being activated, invite_only forums were still registering users
Replaced delegator methods with Forwardable def_delegator in Topic
Allow CAS authentication
If min entropy setting is greater than min post/body length setting, then use a sensible min entropy value instead
A couple of important markdown fixes.
FIX: Markdown references within a list were not working properly.
Better documentation for new Dialect helpers. Migrated emoticon support to new helper format.
Allow basic emoticons to work too.
FIX: 404 on old thumbnails