convert traversal steps test to proper scala test
added support for branch factor restrictions to out, outE, in, inE, both, and bothE, see:
https://groups.google.com/forum/#!msg/gremlin-users/ffJTmmNM5Oo/duCODObB3jsJ
https://github.com/tinkerpop/gremlin/issues/324
https://github.com/tinkerpop/gremlin/commit/3e77de605883751de86adb821acea7c65f465253