Graph primitives2

Hi guys,

I'm following Joey and Ankur's suggestions to add collectEdges and pickRandomVertex. I'm also adding the tests for collectEdges and refactoring one method getCycleGraph in GraphOpsSuite.scala.

Thank you,

semih

Author: Semih Salihoglu <semihsalihoglu@gmail.com>

Closes #580 from semihsalihoglu/GraphPrimitives2 and squashes the following commits:

937d3ec [Semih Salihoglu] - Fixed the scalastyle errors.
a69a152 [Semih Salihoglu] - Adding collectEdges and pickRandomVertices. - Adding tests for collectEdges. - Refactoring a getCycle utility function for GraphOpsSuite.scala.
41265a6 [Semih Salihoglu] - Adding collectEdges and pickRandomVertex. - Adding tests for collectEdges. - Recycling a getCycle utility test file.