Add RTL support to Discourse CSS pre-processing using the RTLit gem and configurable via discourse.conf
ensure rtlit gem in Gemfile is not required by default
ensure RTLit gem is included and CSS is RTLed if css_rtl is enabled in discourse config
Have reciever handle multiple To addresses
Use same reply-to format in all email fixtures
Add error reply for new error
removed usless access modifiers specified in models
Implement SSO overriding avatars.

Implemented by having Discourse download the image from the provided URL
and treating it as a custom upload.

Adds two more parameters to the SSO site’s response:

* `avatar_url` specifies the URL of the overriding avatar.
* `avatar_force_update` Discourse does not re-download avatars that
has already been download from the same URL. Setting this to true forces
Discourse to re-download the avatar in `avatar_url`

Note that both parameters are ignored if `sso_overrides_avatar` is set
to false.
FIX: hanging specs
Improve identity for scheduler
unhack spec
Merge pull request #2669 from akshaymohite/optimization-fixes

removed useless access modifiers specified in models
removed useless assignments at some places
Merge pull request #2671 from akshaymohite/optimization-fixes

removed useless assignments at some places
FIX: unhide post when a moderator undos the flag on which s/he took action
FIX: public_user_custom_fields are returned by UserSerializer
FIX: Don't try and delete inactive admins, rare as they may be.
TRIVIAL: Don't show 06 Aug, show 6 Aug
clarify on flag reply "more" indicator
UX: Show User popup when clicking on a user in the topic list.