Consolidate @javascript tags
Move Transition::Hits::Category to models/view

This lets us reload more easily than lib will
Add a View::Hits::TimePeriod object

Helps with rendering the view, and also allows us to look up
a pre-cooked time period by slug.
Allow selection of TimePeriod for hits
Make no_content_message right for time periods
Remove unused Cucumber steps
Let TimePeriod cope with arbitrary ranges
Correct summary section no_content message
Clicking the hits graph views hits for that date
When looking at a single day of hits, don't display a graph
Pin gem versions
Hide summary sections with no hits
Show a catch-all no_content for summary

* When there are no summary sections with hits, show a no content section for
  the whole summary
Be more imperative about periods
Move date range dropdown out of tabs partial
Move the .date-range class to the dropdown
Fix some JS concerns:

* Don't compare to undefined
* Split out row selection
* Remove redundant window.location.pathname
Include braces in dataTable check
Merge pull request #57 from alphagov/date-range-hits

Selection of date ranges for hits