Always test for presence of lines in grouped timeseries
Added tests for completion rate and completion numbers modules
Moved defaulting of module.axes to defaults
Removed x-axis test because it wasn't compatible with pinned start dates
Be cleverer with determining the period text content if start-at is defined in module config
Remove test for student finance which fails on %-ages > 100
Merge pull request #34 from alphagov/feature/completion-rate-module

Feature/completion rate module