Initial tests, view for builder header title

This is a checkpoint commit for a new view,
``storybase.builder.views.TitleView`` that will eventually be
used to show the title in the header of the builder.

Addresses #578
Remove data links from popup caption

Also refactor caption styles

Addresses #717
Make sure <figcaption> element has text

Make sure an asset's ``<figcaption>`` element has text before
copying it for a popup caption. Some assets may have ``<figcaption>``
elements containing things like a list of datasets, or attribution,
but no caption text.

Addresses #717
CSS classes for asset_id and asset type

Include CSS classes for the asset_id and the asset type in the
asset's container element.  This will facilitate type-specific
styling. It also makes it easier for developers to look up an
asset when viewing front-end display of information.
Hide popup captions for YouTube videos

The popup captions look weird over YouTube videos, especially
since the video embed is fixed-width.  Hide them using a CSS
style matching the ``asset-provider-youtube`` class.

Addresses #717
Don't send site contact notifications from user address

Instead, send them from ``settings.DEFAULT_FROM_EMAIL``.

Sending from the user's email address was causing the message to
get rejected by the GMail SMTP server when the user's address was
a GMail or Hotmail (and perhaps others) address because the sending
SMTP server wasn't GMail's or Hotmail's.

Closes #886.
Update tests for #886 changes
Remove circular imports from Haystack signal processor

See http://stackoverflow.com/a/17364366/386210

Addresses #887
s/ugettext/ugettext_lazy/
Merge branch 'develop' into 578-rework_story_information
Toggle editor display and save model in TitleView

In the Backbone view for editing the story title, toggle the
display of the title and the text input on blur and when the
Enter key is pressed and released.  Also set the title attribute
on the model to the new value of the input.

Automatically save the story model when its title attribute
changes.

Refactor the test code to be more DRY.

Addresses #578
Add character counter to TitleView

Addresses #578
Further refinement of header title editing

This is a checkpoint commit.

* Wire ``TitleView`` into AppView
* Logo as an <img> instead of as a background CSS property. See
  http://csswizardry.com/2011/08/more-logo-markup-tips/
* Separate logos for template selection view vs. story editing view
* Make title font in builder match the title font in viewer
* Give title editing input focus when title is clicked.
* Event handler that does saving of story in TitleView because
  signature of ``change:title`` event is different than that of
  ``Model.save()``.
* Hack to disable caching of LESS when using less.js on non-localhost
  hosts.

Addresses #578