Update to version 1.3

1.3 (2020-08-18)

- Add option to use Garlerkign Least Squares (GLS) stabilization
- Allow for different chi_tilde on boundaries
- Add option for multiple mesh regions:
    - Allows for different Knudsen numbers in regions
    - Add new example: Lid-driven cavity with two mesh regions
- Optimization of CI pipeline and scripts in Gitlab:
    - Assert Flake8 compliance
- Add option to output solution vectors (for model order reduction experiments)
- Improve README with R13 equation set and list of features