Added model for front-page news items

Addresses #567
Don't install all the development requirements.

The travis build was timing out, so just install Fabric to limit the time
it takes to download and build dependencies.

Addresses #569
Merge branch 'develop' into 567-editable_news
Added a field to toggle news is on homepage

Addresses #567
Wire up dynamic news on homepage

Instead of hard-coding news, use the new NewsItem model to display
news on the homepage.  Remove the hard-coded news items from the template
and their assets from the static directory.  The rendering of the
featured_news is accomplished through a new featured_news template tag.

Closes #567
Add cssselect as a dependency.

It is needed by the way we use lxml, but at some point got broken out as
a separate package form lxml.

Addresses #564
Enable JDK for Travis build

Solr was complaining about a missing JDK.

Addresses #564
Remove duplicate wget lines

Addresses #564
Debugging messages for Solr on Travis

Addresses #564
Tell Jetty about the JDK

Addresses #564
Travis Solr debugging

Addresses #564
Point Jetty/Solr to correct Java on Travis

Addresses #564
Point Jetty at correct JDK

Setting JAVA_HOME didn't seem to work.  Trying to set JDK_DIRS.

Addresses #564.
Fix sed command from last commit

Addresses #564
Cleanup Travis build debugging

Closes #564
Merge branch 'develop' into 520-viewer_asset_border
Resize figure to wrap iframe

Previously, the figure was only resized to fit images, but I noticed that
it looked a bit odd with video content as well. YouTube seems to be the
most common video provider, and it uses IFRAMEs, so I modified the
figure-resizing code to size the figure captions and borders to wrap
IFRAMEs as well.

Addresses #520.