The two methods `StreamEntriesHelper#stream_link_target` and
`StreamEntriesHelper#acct` are based on checking whether we are running
in an embedded view.

This adds some test helper code to make the testing easier. We extracted
some "magic strings" to constants to lower the coupling in the specs.

The code that generates CSS is based on a lot of boolean conditions.
The possible combinations of these grows exponentially as we add more
conditions.

Since most of the code is conditional on a single boolean, we tested the
following:

1. All `false`
2. All `true`
3. Each individual flag set to `true`

The methods tested are:

* `StreamEntriesHelper#style_classes`
* `StreamEntriesHelper#microformats_classes`
* `StreamEntriesHelper#microformats_h_class`

We used some random Arabic characters to test that the various RTL
conditions got triggered.

* significant improvement in microformats markup

This is a huge improvement and I believe will close #965.

Had these microformats reviewed by others in the community to help
ensure they are at least correct, if not complete.

I did not want to change the structure of the page, and so there it does
not fully mark up the entire ancestry chain, or reply chain, only the
direct decendants and direct ancestors are correctly associated, but
this is likely fine as the most important bit is to have access to the
urls for those toots which are now correctly fetchable.

* improve code climate

* trying to pass code climate tests

* code climate

* fix p-summary for content warning posts

* fix error introduced when merging via github

* Remove trailing whitespace

* Use query methods instead of explicit .blank? checks

* Add coverage for embedded status view

* Refactor embed view to eliminate @external_links variable

Removes:

- avatar_for_status_url
- relative_time
- reblogged_by_me_class
- favourited_by_me_class

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.

fix #361 with rich OEmbed display via iframe, fix #237 by hiding sensitive
content behind a spoiler on public pages

for avatars/headers, resize avatars down to 120x120 instead of 300x300. Set cache headers on S3 stuff, also
make it private (aka only accessible via expiring links to prevent hotlinking)

by updating it at least every 24h if the user visits the site

Added stack trace for SQL queries in development
Removed badly thought out accounts/lookup API

relations on Status#mentions

simplify FanOutOnWriteService, add /api/accounts/lookup method

POST /api/statuses                  Params: status (text contents), in_reply_to_id (optional)
GET  /api/statuses/:id
POST /api/statuses/:id/reblog

GET  /api/accounts/:id
GET  /api/accounts/:id/following
GET  /api/accounts/:id/followers
POST /api/accounts/:id/follow
POST /api/accounts/:id/unfollow

POST /api/follows                  Params: uri (e.g. user@domain)

OAuth authentication is currently disabled, but the API can be used with HTTP Auth.