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