add ability to open status by URL from search (fix #53)

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 issue with detailed status view not supporting unreblogging/unfavouriting

status is not in the system at time of distribution; fix #607 - reset privacy
settings to defaults when cancelling replies

Try to fix Travis CI setup

Federate spoiler_text using warning attribute on <content /> instead of a <category term="spoiler" />
Clean up schema file from accidental development migrations

with YAML-defined defaults. Add admin page for editing global settings. Add "site_description"
setting that would show as a paragraph on the frontpage

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

Reflect "requested" relationship in API and UI
Reflect inability of private posts to be reblogged in the UI
Disable Webfinger for locked accounts

Filters out hidden stream entries from Atom feed
Blocks now generate hidden stream entries, can be used to federate blocks
Private statuses cannot be reblogged (generates generic 422 error for now)
POST /api/v1/statuses now takes visibility=(public|unlisted|private) param instead of unlisted boolean
Statuses JSON now contains visibility=(public|unlisted|private) field

Fix #233, fix #268