Add `Road#obstacles_part_of_a_collision(action)` to help construct features.

[dmorrill10]

Move code from lines 154 to 163 to this new method. You'll also have to create an updated Car, as is done on line 125, and loop over obstacles in self._obstacles.

[dmorrill10]

Have it return both the list of obstacles and the list of obstacle indices.

[dmorrill10]

Let's ignore this for now.