v0.2.0

Release version 0.2.0

### Added
- `test3`: collision detection with [cute c2][].
- Number of cusps statistics.
- Histogram plots.
- Different costs tests.
- Test of switching street movement to parking movement (`test7`).
- `test8`, `test9`.
- [BrainTree][] single header library.
- Test of switchout between road movement and parking (`test10`).
- Tests 15, 16, 17, 18 -- 2D, 3D grid and k-d tree.
- Script for generating simple JSON scenarios.

[cute c2]: https://github.com/RandyGaul/cute_headers/blob/master/cute_c2.h
[BrainTree]: https://github.com/arvidsson/BrainTree

### Changed
- Refactor plot scripts.
- Refactor template JSON output.
- Update test template to include parking slot planner (enables loading JSON
  scenarios without goal positions, just slot).

### Fixed
- Plots.