Mention the manual extension upgrade in the version error message.
Changed the look of userstreams and standalone annotation page.

Fixed allignment issue with hypothes.is logo in topbar.
Changed font to san-serif font.
Fixed quote allignment with annotation.
Updated link to extension on displayer.pt
Merge pull request #705 from hypothesis/Userstream-2

Changed the look of userstreams and standalone annotation page.
Add workaround for 3rd-party content blocking problem (#634)
Relax the time limit for the version check, and offer instructions for updating the extension.