Move form-wide response error code to formHelpers

Add an (optional) third argument to the method
`formHelpers#applyValidationErrors()` that can take an error string,
``reason``, to set on the form itself, rather than any particular
field. Remove the duplicate code in the auth directive to reset
the response errors on each field, which is handled already in the
``form-input`` directive.
``form-input`` should not render inputs on change

Fix #1490
Remove dead share code

@aron if those tooltip attributes are used somewhere I can't find
them so please correct me, sorry.
Hide the footer for unsaved annotations
whitespace
Remove a few href="#"

In Angular, this is better expressed as href="" because that makes
Angular prevent the default automatically.

https://code.angularjs.org/1.1.5/docs/api/ng.directive:a
Upgrade AngularJS libs
Merge branch 'angularjs-xss-hotfix' into v0.3.x
Tagging v0.3.2
Merge tag 'v0.3.2'

Hypothes.is 0.3.2

Conflicts:
	CHANGES.txt
Fix a bug in tabReveal directive

That syntax was not what I thought it was and had nasty issues when
there were no panes.
Add KaTex math rendering

Add KaTex javascript, CSS, and fonts to vendor folder.

Create a renderMath() function that parses sanitized markdown for math as denoted by '$$'

Modify ctrl.$render to first sanitize the markdown and then renderMath. Newly rendered
math is then trusted as HTML becuase otherwise ngSanatize removes crucial style attributes
that leave the math unreadable.
Add MathJax fallback

If KaTex math rendering throws an error, load MathJax from the CDN and render
the math with MathJax.
Merge branch 'math-support' of https://github.com/hypothesis/h into math-support

Conflicts:
	h/static/scripts/directives/markdown.coffee