Steps toward fixing the shooting mover.

There's a problem that one-way shooting gets stuck when you have a 3-frame
trajectory. This probably means that we're not really shooting from the
frame we think we're shooting from.
I think I fixed it.
Commented debug setattrs in shooting movers
Remove ipynb used to play with debugging this.

Useful for it to have existed in case anyone needs to debug this sort of
thing before, but doesn't need to hang around master.
Mostly correction in dynamics_engine.

Previously, we didn't check whether the first snapshot already hit the stop
condition.

Also resurrected fix_shooting_mover.ipynb, and some visual cleanup in
pathmover.py.
Now it works! Next undo any unneeded changes.
Undid some unneccessary changes.
Removing the fix_shooting_mover.ipynb.

Useful for debugging, shouldn't be needed now.
Merge remote-tracking branch 'upstream/master' into shooting_fix
Merge pull request #96 from dwhswenson/shooting_fix

Shooting fix