Add missing currency option to stub
Use relative links
Stop "more info" links opening in new tab - request from Phil
Update intro wording, add link to CloudStore itself
Hard-code showing last 12 events, not 21, in completion rate graphs.

We should stop hard-coding this, and follow the same logic as other graphs, soon
Remove null data from series altogether.

Update tests to ensure that null data is ignored - basically we want to treat
it as missing data.
Stop x-axis labels overlapping at 900px
Stop all related links opening in new tab (really)
Fix styling on graph legends.

When .summary is not present, float legend left. When .summary is present, fill space available.
Reduce size of y-axis ticks under 640px to stop currency symbols vanishing in FF