v0.2.0

Release version 0.2.0

### Added
- Parking slot class, parking slot info methods.
- Bicycle car `<<` operator.
- Parking slot `<<` operator.
- Collide functions (`intersection`, `inside`) moved from `psp` library.
- Collide function (`collide`) detecting if two polygons collide.

### Changed
- Make `sgn` function available in api (moved to header file).
- Use references instead of pointers in `bcar` library.