Updates to sorting and mean calculations

Refactoring to sorting and averaging to fix some bugs in the new front page charts.

I also added a showPoints() function to LineSeries to make the points optional. Longer term, this could take an options argument for how the points should be displayed.
Small point of habit for testing, but an assertion should only ever be followed by more assertions or teardowns. If you are adding new code, its better to split out to a new test. This looks like we want one for averaging, one for filtering, and one for setting a new filter.

Also, the //Given is usually paired with a //When and/or //Then :)