Adding required collection options for rendering graph axis.
Adding axis labels for live-service-usage (sparklines)
Lint fixes for visitors realtime collection
Tables were rendering 'no data' for falsy values.

They don't do this anymore.

Added test to cover this.
Added new stub json for accessible tables in graphs.
Merge pull request #222 from alphagov/feature/accessibleVisitorsRealtime

Feature/accessible visitors realtime