Implement the two pending specs on `Status`: `reblogs_count` and
`favourites_count`.

These are currently user facing errors, but are not localized. This adds the
ability for these messages to be localized.

This implements all pending specs, and adds additional coverage for the
following functionality:

* Normal status creation
* Creating a reply status
* Creating a sensitive status
* Creating a status with spoiler text
* A status with no spoiler text gets an empty string for spoiler text
* Creating a status with custom visibility
* Creating a status for an application
* Processing mentions
* Processing Hashtags
* Pinging PuSH hubs
* Crawling links
* Attaching media

Checking reblog vs original status was happening in multiple places
across the app. For views, this logic was encapsulated in a helper
method named `proper_status` but in the other layers of the app, the
logic was duplicated.

Because the logic is used at all layers of the app, we extracted it into
a `Status#proper` method on the model and changed all uses of the logic
to use this method. There is now a single source of truth for this
condition.

We added test coverage to untested methods that got refactored.

There are currently not specs for the two media validations that are performed
by `PostStatusService`. This adds specs for the validations that ensure that you
cannot attach more than four files, and that a status cannot have both image and
video attachments.

This adds the ability to filter user signup with a whitelist
instead of or in addition to a blacklist.

Fixes #817

Fix anchor tags in some wikipedia URLs being matches as a hashtag

StreamEntry model. Simply render Salmon slaps as they are needed

if account lock info was up to date, otherwise re-do the FollowService
with now updated information

Try to fix Travis CI setup

redis-backed "mentions" timeline as redundant (given notifications)

affected, replaced onClick handler with onMouseUp/Down to detect text
selection not trigger onClick handler then

application website validation, don't link to app website if website isn't set,
also comment out animated boost icon from #464 until it's consistent with non-animated version

A couple of places were using "reblog" rather than "boost" - this updates them to match the web UI