Angular upgrade v1.2.13

Deleted line that caused the sign in section of the topbar to be abnormally large

In Angular v1.2 what has actually changed about isolate scopes is that
only the directive declaring isolation gets the isolate scope. Its
template will inherit this scope, but other directives on the element
will not. That's the reason ngModel now works with `$parent`.

Everywhere we were binding the controller to the scope it's easier to
use the isolate binding with `=ngModel`.

The isolation scopes are truly isolated better, or evaluation
of the submit handler is happening from the descendent cousin
scopes of the isolated directive. I could probably have moved
the ng-submit handler below the authentication directive, but
I didn't see a compelling reason for the directive to stay in
an isolated scope.

This moves away from measuring layout of non-typographical elements
in ems, favoring px for better consistency across devices with different
pixel densities. While that may sound backward, the reality is that CSS
pixels are device independent, and non-integer em values seem to be handled
less consistently.

Finally, there were some font size and line height tweaks made here to match
the new measurements of the top bar. This provides a consistent feel to the
top bar across devices and dpi.

Added loading icon suggestion and basic CSS.

Added contributing information and useful resources to the homepage.

Changed icons to give them a consistent style.

Changed positioning on topbar to fixed on the streams page. It's much more consistent with design on feed-type sites like Facebook and Twitter.

See #1020 for a description of the problem.

This commit patches the merge behavior of the bridge plugin:
never update a list of targets with a shorter list.
(This avoids it being zeroed by accident.)

This does not really solve the more generic problem: the race condition
of the messages moving on the bridge. We should either do some
time-stamping, or some other smarter flow control...

Fix #575

Changed how threading works.

Conflicts:
	h/js/services.coffee

Updated Annotator TextHighlights plugin to  c90ac7cd (typed packaging branch), with performance improvements

Fixes #972