Make Hits::Category fill in zero days

Google charts will interpolate from zeroes otherwise,
creating misleading slopes in charts.
Fix Jasmine/cuke tests for new DataTable
Get rid of global rawData dependency
Make no_content show the right thing
Category index errors on not found
Fix grouping for "other" category

* group correctly in controller
* Be defensive about this to avoid future mistakes

Was grouping incorrectly on date and status, which
led to Category#insert_zero_hits operating on the
incorrect assumption that there was one hit row per
day, hence losing data and not showing enough volume
on graphs.