Fixed termination condition for the planner

Evan reported that the planner was occasionally returning invalid
trajectories if it timed out. I switched the termination condition to
explicitly check whether a solution exists instead of relying on the
return value of solve().
Call setup() on SpaceInformation in the simplifier

This was causing the simplifier to use an incorrect (and very low)
resolution for collision checks. In many cases, this meant that the
resulting trajectory would be in collision.
Added simplification to demo script.