* Add spec for media controller

* Add MediaAttachment.attached scope

* Simplify methods in media controller

(Because postgres can tell that count(*) needs no extra checks, but
counting a specific column requires them)

before. In the API, attachments now can be either image, video or gifv. Gifv
is to be treated like images in terms of behaviour, but are videos by file
type.

fix ProcessFeedService pushing status into distribution if called a second time
while the first is still running (i.e. when a PuSH comes after a Salmon slap),
fix not running escape on spoiler text before emojify

for local attachments, use them in URLs. Check status privacy
before redirecting to actual file.

Do not autoplay videos, display play button instead. Use expiring links when using S3. Do not keep originals
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)

to the API

Using `-strip` cli options from ImageMagick

http://www.imagemagick.org/script/command-line-options.php#strip

fix #85

timeline reload in UI, other small fixes