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.
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.