agarie/measurable — pull request #11 by rossta (2014-04-02 12:01:33+00:00)
Title: Update implementation of jaccard_index

Uses set operators to find intersection and union of given enumerables.

Directly maps to the [definition of Jaccard Index](http://en.wikipedia.org/wiki/Jaccard_index), at least according to Wikipedia.

Fixes agarie/measurable#10