Embed widget height attribute needs 'px'

Addresses #529
Merge branch 'master' into develop

Conflicts:
	README.rst
Use ChromeDriver for in-browser testing

Firefox is broken right now and more Floodlight users use Chrome anyway,
according to analytics.
Pause a bit to allow story to auto-save
Clean up integration tests for storybase_story app

These tests were written against the wireframe theme so some of the
tests were failing against the current theme.
Override flexslider left/right nav arrows z-index on homepage so that that they do not obscure the megamenu.
Change tabs to spaces in homepage.less. No changes to content.
Promote h5 titles in featured_object to h3 -- reads better; seems semantically more appropriate. Tweak spacing between image and text in featured_object (on homepage, anyway; might want to move those styles elsewhere to make them globally applicable).
Clean up in-browser and integration tests

Many of the tests were broken since the theme for the different detail
pages was added.  Some of the tests that reflect functionality that is no
longer part of Storybase, such as asset detail pages, were removed.
Merge branch 'develop' into 433-homepage-redesign
Merge remote-tracking branch 'eric/433-homepage-redesign' into 433-homepage-redesign