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
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
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.
(For now) don't show error popup

Suppress the error popup window for uncaught JavaScript errors. It's
showing up for all uncaught exceptions, even ones that aren't critical
failures. We should hide this until we have a better way to make it less
obtrusive or only show it for truly critical errors.

Work-around for #634
Include page location in JavaScript error log.
Update changelog
Merge branch 'hotfix-634-turn_off_error_popup' into develop

Conflicts:
	README.rst
Add Google Analytics campaign parameters

Add Google Analytics campaign parameters to banner links.

Addresses #198.
Merge remote-tracking branch 'origin/develop' into 198-homepage_banner
High-level query API for connected stories

There were a lot of complicated, difficult to understand ORM queries to
select or exclude featured stories.  After reading
[Building a higher-level query API: the right way to use Django's ORM](http://dabapps.com/blog/higher-level-query-api-django-orm/),
it seemed like using custom QuerySet and Manager implementations was a good
way to make view code more independent from the ORM, to make queries
more readable, and to make queries more DRY.

I added a custom QuerySet class, StoryQuerySet, for Story models that has
methods that let you find connected, normal and seed stories. I also
implemented mixin classes in the storybase.managers module that are mixed
in to StoryQuerySet to select stories that are flagged to be on the homepage
and stories that are published.

The methods of StoryQuerySet are proxied to StoryManager.  Also,
StoryManager returns a StoryQuerySet, which means that Story.objects.all()
will be a StoryQuerySet.  The use_for_related_fields flag is set for
StoryManager, so the custom query set methods should be available across
relations as well.

There are a number of places in the code where the custom query set methods
can be used to clean up the code and this should be done in future commits.
Merge branch '198-homepage_banner' of github.com:ghing/atlas into 198-homepage_banner
Make the "random" banner strategy the default