Make replies default to privacy settings of the status being replied to

Fix #635 - Include the initially-reported status in report UI even if it's not
among the user's most recent statuses

I haven't had a chance to test this, because I don't currently have a fully functioning computer I can set up a dev-environment on, but this *should* make it so when a user toggles a post to be private, a disclaimer appears clarifying what "private" really means.

Add variable for text of privacy disclaimer

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

Refresh timelines when streaming API reconnects in the UI

to only those from local users; Add link to "extended information" to
getting started in the UI; Add defaults for posting privacy; Change
how publish button looks depending on posting privacy chosen

Try to fix Travis CI setup

warning mentions preview into area where actual content would be

overshadow requirement for remote-lookup

untested, my vagrant is bugged again, submitted at gargron's request

work flawlessly was a nightmare). WARNING: This commit makes the web UI connect to the streaming API instead
of ActionCable like before. This means that if you are upgrading, you should set that up beforehand.

sounds complex, but really it just reorganizes the posting options and
adds a seperator line

they have been loaded and favourited/reblogged from another source

Since the status JSON returned from public/hashtag streams does not
contain favourited/reblogged attributes, merging them should not
override existing ones.

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

Changing the way the background image is positioned and the box is sized should fix problems with the text overlapping the image on mobile browsers and Edge.