Add Unit Tests for PlanToBasePose() and example code

[DavidB-CMU]

Should SBPL be a required or optional dependency for HERBpy?

The example code uses PlanToBasePose() - how should I make a Unit Test for this if? If SBPL is a required dependency then it is easier.

[mkoval]

I agree with this entirely. However, I think these tests should be on SBPLPlanner and live in prpy. We should add or_sbpl as a <test_depend> like we did for the other planners that we test in prpy.

@DavidB-CMU Can you move this issue there?

[DavidB-CMU]

Issue moved to prpy personalrobotics/prpy#268