Add fixtures and tests for outliers when we expect a result
Add method for computing weighted counts of clusters

Also included is a test for this new method. This is meant to remove the
following from Serrano:

https://github.com/cbmi/serrano/blob/2.x/serrano/resources/field/dist.py#L152-L174
Merge pull request #100 from cbmi/weighted-count

Add method for computing weighted counts of clusters