v0.3.0

Release version 0.3.0

### Added
- Collision detection based on [cute c2][].
- Time restriction for algorithm.
- RRT node types (currently `cusp` and `connected`).
- Compound extensions.
- Dijkstra algorithm for path optimization (`rrtext3.cc`).
- Grid based `nn` and `nv` methods (`rrtext4.cc`).
- Compound extensions.
- JSON output.
- Should continue method.
- Deinit method -- get ready for planner reset.
- JSON input.
- JSON output.

### Changed
- How the algorithm is stopped - possible to choose from more options.
- Separate `store_node` procedure.
- Grid constants used in `ext4`.
- Some small refactoring.

### Deprecated
- `should_continue` method.

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