Tag release v0.2.0

Tag release v0.1.1

Wall avoidance system (amethyst#71)

* Adding `ClosestObstacleSystem` to tag any creatures near walls w/ Closest<Obstacle>.
SeekSystem<Obstacle> will help the creature avoid that obstacle.
* Adjusted SeekSystem behavior to be a little more configurable.
- SeekSystem<Obstacle> now tries to follow the wall rather than run away.
- Adjusted how close the creature can get to the wall.

Merge pull request amethyst#24 from marot/23-missing-dependencies

update README.md to inform users about necessary dependencies on linux