Much nicer posts settings sheet.

From The Dave's mockup. Closes #200
Separate rows and left-align font size in posts settings sheet.
Fix compose view on iPhone running behind the keyboard.
Don't animate compose text view when dismissing.
Formatting.
Fix Gas Chamber JSON parsing.

Seems to be a server-side bug. Reported it a month ago, but forgot to work
around it in Awful.
Shrink corner radius for theme buttons.
Fix app icon on awfulapp.com
Fix parsing PM reception ability from posts.

Unlike profile JSON, users in posts JSON don't have a "receivepm" value.

Fixes #202.