Add /dev/emails page for testing email output
Rework copy for the reply notification
Add an html variant of the reply_notification email
Add html variant for the notification emails
Add a TemplateRenderException

This allows the template rendering to catch known rendering issues
and handle them accordingly. Such as having no record of the
notification recipient. All other exceptions now pass through.
Raise the error if a notification fails to send
Add tests to validate the email notification content
Ensure wording is consistent in notification email
Do not catch any exceptions in the notifier
Fix example notification email text

Remove unused template variables.
Fix height typo on target.pos property
Remove the tooltip on the timestamp

Now just uses the default browser title functionality.
Always right align timestamps in cards

Move dropdown to the left of the timestamp to ensure timestamps are
always in line. Vertically align the baseline of the timestamp with the
username.
Remove dashed border on collapsed threads

It left a single pixel, which looked like a rendering glitch.
Clean up blockquote styles

* Remove cartoon quotes.
* Use a class rather than styling all blockquotes.
Correct expand/collapse icons on thread

Now collapsed items have a plus sign and expanded ones a minus. This
brings it inline with other tree view implementations such as those
found in Windows and Reddit where the icon represents the action
rather than the current state.
Merge pull request #1409 from hypothesis/fix-annotation-typo

Fix height typo on target.pos property
Fix line height on heatmap pointers
Drop tagit in favor of ngTagsInput
Move common form styles into mixins