Encapsulate action stats

This gets rid of a bunch of instance variables in the view/controller
layer.
Move time to complete stats into separate class

This separates out the calculations from the queries so we can get
decent tests around them.
Extract time to complete partial
Move calculation out of view
Don't round in ttc.min_sec method

This fixes a bug where it would round 1.8 days up to
2 days, and still display the extra hours in addition.
Make test name reflect actual data
Merge pull request #168 from kytrinyx/stats-actions

Encapsulate the stats for actions on the stats index page