UX: Make category link text black in digest emails
Automatically include all `.hbs` files from plugins
Allows us to easily define routes in plugins
Move `register_asset` into `PluginRegistry` -- the logic works better
there.
[bug fix] When recovering a post, at times the topic related to the post still returns nil.
Use the with_deleted method to include topics that have been soft deleted so that they too can
be recovered.
When using automatic file includes (es6, hbs) from plugins, allow the
asset pipeline to find new and deleted files with deleting the `tmp`
folder and restarting the server.
add embedding notes to admin quick start
add embedding notes to install doc
Update INSTALL-digital-ocean.md
show ungrouped emojis in tab, remove a few aliases

(I dislike :shit: and :squirrel: made no sense)

TODO: stop using symlinks for aliases
PERF: optimise rendering of posts
do we need #list-area margin-bottom so big?
FIX: properly unescape HTML entities in excerpts
FIX: Text in select2 dropdowns should not be variable since the
background is always white.
UX: Banner topics should be readable even with dark color schemes.
Update username should return a json response

- Have update username return json response that contains the updated
  username and id. I figured this would be better than just return "OK".
- Add test to verify that the new username is returned.
PERF: don't render user card until displayed
PERF: don't render share dialog until we have a link.
PERF: don't render composer until we need it
FEATURE: support for emoji sets

Added following emoji sets
  - Apple/International
  - Emoji One (default)
  - Android/Google
  - Twitter

FIX: translations from plugins weren't properly merged with default translations
FEATURE: new 'site_setting_changed' event