Features:
- `target_positions` are now in `agent` space. See `coords_systems.md`
  and notebooks for examples on how to use it and its relation with the
other spaces. This fixes a misalignment which is affecting the
competition;
- Ego and AgentDataset now returns more matrices to convert between
  spaces;
- Transformations Matrices notation has changed from "A_to_B" to
  "B_from_A";
- BoxRasterizer now support subpixel precision;
- Fix an issue with swapped width and height which was preventing to use
  rectangular-shaped inputs;
- introduce Pipenv for deterministic builds;
- Add option to disable traffic lights;
- Improve trajectories visualisation params;

Known Issues:
- SatelliteRasteriser output is wrong for rectangular-shaped rasters;
- Calls to get_frame_indices might be slow (a solution is currently
  being tested);