Fixed a bug in the way we're playing forward functions in x and xd. The interface isn't at nice currently, but it's more correct. The unit tests are very exact. Also realized that the intermitent oscillations were happening because of computational limitations. The number of integration steps was still set to 10000. Reduced that to 100, and reduced the number of evaluations per integration to the same. The demo is now evaluating at each integration step and the size of the integration dt matches that of the evaluation lookahead dt.