Remove orange button from legal agreement view

The form validation (and eventual event triggering) is now triggered
when the checkboxes are checked rather than when the form is submitted.

Addresses #515.
Add numbers to the publish view steps

Add numbers to the publish view steps. I did this by making each
sub-view's element a ``li``.  I had to do a bit of CSS trickery to style
the ordered list numbers to match the headings.
http://www.456bereastreet.com/archive/201105/styling_ordered_list_numbers/
was very helpful with this.

I still need to test this under IE.

Addresses #515
Use LESS variables for publish step number styles

This is a tweak to the changes made in 2a8bcadaa92e1417c09d52e3053383b12115f325
that uses LESS variables to make the publish step numbers match the
header styles instead of hard-coding values.  This should make the code
more future proof.

I added a ``@styled-header-family`` variable to variables.less and also
use this variable to set the font in the ``.styled-header`` mixin in
base.less.

Addresses #515
Merge branch 'develop' into 515-publish_cleanup
Merge branch 'develop' into 515-publish_cleanup
Refactor publish step views

There was too much logic in the publish step templates and too much
logic related to toggling various elements based on publication status
in PublishView.  I broke most of the UI elements such as the publish
button, the to-do list and the view/publish buttons into their own views
and broke out common utility methods and initialization to a base view
class.

Addresses #515
Tests for PublishButtonView and PublishTodoView

Addresses #515
Merge branch 'develop' into 515-publish_cleanup
Tests for PublishedButtonsView

Addresses #515
Merge branch 'develop' into 515-publish_cleanup
Make get_default_img_url_choices a class method

get_default_img_url_choices and get_default_img_url don't touch the
instance object, and should return the same value for all instances, so
they can be a class method.  Doing this lets me bootstrap a value into,
say, a Backbone view without having a model instance.
Upgrade Backbone and Underscore

Upgrade Backbone and Underscore libraries to most recent version.

Backbone goes to version 0.9.10 and Underscore goes to version 1.4.3.

This is mostly because I wanted to start binding to events on models and
collections, when possible, instead of the event bus.  As of Backbone 0.9.9,
there are now listenTo and stopListening methods on Events, which make
binding event callbacks a little cleaner.

Note that in this version of Backbone, the Backbone object extends
Backbone.Events so it can be used as a global event bus.  Doing this might
make the code less verbose in the future.

I had to change the Asset model validation test to reflect the way that
validation doesn't automatically happen on Model.set and that invalid data
sends the "invalid" event rather than "error".
Checkpoint commit for new featured asset views

Addresses #515
Merge branch 'develop' into 515-publish_cleanup
Rebuild CSS

I forgot to rebuild CSS in c0cf382265c5620e1d0be26180526980a7ee55f9

Addresses #515
Merge branch 'develop' into 515-publish_cleanup
Trigger a 'set:featuredasset' signal

I want to move away from relying on the event bus (this.dispatcher in most
views) and try to trigger/listen-to events on the models and collections
themselves when that's appropriate.

To this end, the Story.setFeaturedAsset method now triggers a
'set:featuredasset' signal when the featured asset is set.
Implement switching between featured asset views.

Implement the views and logic that display the correct view depending on
whether the user is viewing, selecting or adding the featured image.

Also in this commit, I fixed a bug that I think is related to the
Backbone upgrade.  SectionEditView now only renders its subviews on a
"sync" signal, not on both "sync" and "reset".  I believe that in the
new Backbone versions, both events are triggered when a collection is
updated from the server, causing extra copies of the SectionAssetEdit
subviews to be created.
s/this/that/

``this`` isn't bound to the view instance in the context, ``that`` is.
We want ``that``.
Merge branch 'develop' into 515-publish_cleanup