Improve mobile readability by putting whitespace between messages, not lines

This generally removes a lot of whitespace on mobile while still improving readability
In particular, it makes it easier to see which lines belong together
Double-tap escape to disconnect
Highlight user when clicking their nick
Merge pull request #256 from lorenzhs/doubletap

Double-tap escape to disconnect
Merge pull request #255 from lorenzhs/lineheight

Improve mobile readability by putting whitespace between messages, not lines
Merge pull request #257 from lorenzhs/nickclick

Highlight user when clicking their nick