CHANGES:

1. Introduced default unit traffic flow;
2. Removed old test data from data directory.  This now contains real static data only.
3. Brought README.md up to date.
4. Removed extraneous files from root project directory.

Ruffus pipeline

See merge request !16

Deleted example_config.yaml, medium_term.yaml, medium_term_prediction.py, poetry.lock, simulate.py, within_between_config.yaml, tier_info.py files

CHANGES:

1. Committed missing `case_data.py` file
2. Moved pipeline specification into `covid.ruffus_pipeline`
3. Moved pipeline initialisation into `covid.pipeline`

CHANGES:

1. Replaced `read_phe_cases` with `CasesData`
2. Column-name fix in `case_exceedance`
3. Fix column heading in `summarize.infec_incidence`
4. Add Rt_exceed to `summarize.rt`
5. Add layer option to `summary_geopackage`
6. Update `ruffus_pipeline.py` to reflect above changes
7. Update `template_config.yaml` to reflect above changes