Try to fix Travis CI setup

nested inside a common parent (<Account>), instead they all embed <HeaderContainer />

for extremely wide monitors

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

now return empty hash instead of throwing a 404 error. When following,
merge into timeline will filter statuses

in the column and what appears as desktop notifications. Settings do not
persist yet

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 #205, fix #156, fix #124

Fix #233, fix #268

skip ActionCable for follow/unfollow/block events, instead clear UI from
blocked account's posts instantly if block request succeeds. Add forgotten
i18n for sensitive content