Removed stale home page listing code.

I removed the Django CMS plugin code because they're no longer used and I
think that the template tag approach that we've taken lately is nice
because it's more CMS agnostic.

I removed some of the helper functions for rendering the plugin output since
they're also no longer used and that logic seems better encapsulated in
template tags.

Addresses #198
Explore page: story titles should be left justified. (#576)
First pass at homepage banner

This is a first pass at the homepage banner implementation.  It doesn't
implement any kind of background generation or caching and currently only
selects stories randomly.

Still to do:

* Background rendering and caching
* Other strategies for selecting stories
* Registration pattern for different story selection strategies and method
  on the registry for selecting the different strategies or a random
  strategy.

Addresses #198
Wire in story links.

Forgot to replace the dummy links when I did my first pass of the
homepage banner feature in eb3719e02a4e90fe804df96633f289e0dc17c86c

Addresses #198
Show user an error message on uncaught exceptions

Addresses #623
Merge pull request #620 from patternleaf/576-left-justified-titles

Explore page: story titles should be left justified. (#576)
Update changelog.

Update changelog to mention fix for #576 that @patternleaf implemented
in 418a38e21951b8251aaface0756d65ebeefbe262
Use imagesLoaded plugin to detect image loading

Use the imagesLoaded jQuery plugin to detect when images are being
loaded to trigger our handler to resize the image containers and
captions.

Closes #622
Merge branch 'hotfix-622-scale_viewer_image_borders' into develop

Conflicts:
	README.rst
More robust search for django-admin.py

The apply_djang_patches script called from ci_before_script.sh started
failing in the Travis CI build.  The reason was that django-admin.py
wasn't being found.  Try executing the script directly, instead of being
called with ``bash`` from ci_before_script.sh and try explicitly activating
the virtualenv from ``apply_django_patches``.

Addresses #626
Log uncaught JavaScript errors to the server

Addresses #623
Merge branch 'hotfix-623-catch_js_errors' into develop

Conflicts:
	README.rst
Merge branch 'develop' into 198-homepage_banner
Registration pattern for banner implementations

Provide a registration pattern for different banner implementations.

The ``banner`` template tag now takes ``banner_id`` as an argument to
select a particular banner implementation and keyword arguments that
are passed to the individual implementations.

If ``banner_id`` isn't specified, a random banner is selected.

Addresses #198
Banner implementation selecting stories by topic

Addresses #198
Debugging for Travis build

Addresses #630
Point Travis Jetty at correct location of JDK

Addresses #630
Merge branch 'develop' into 198-homepage_banner
Added a ga_campaign_params template tag

Added a template tag for generating the query parameters for a Google
Analytics Custom campaign.

I'll need this to support analytics and A/B testing with the banner.

In order to test this, I refined the SettingsChangingTestCase.
Clean up use of SettingsChangingTestCase

Use the set_setting method instead of this sloppy setting changing
set up.

Also, the inheritance order was whack, even though it didn't really matter
in this case.