Create test cases for custom motif finder

[bestchai]

Custom motif finding (aka user defined motif finding) has been implemented, but no tests have been written.

Due to its complexity, defining test cases by hand probably isn't the way to go. Instead, there should be a "framework" for creating test cases. There should be a system that allows developers to automatically generate a test case by defining a motif, the graph to search on, and the expected result.

[Issue created by pqperry: 2014-08-18]
[Last updated on bitbucket: 2014-08-26]