Override table heading attrs

[dsrees]

Description

Issue #263 - Overriding attrs for table heading

• Renamed table.col.attrs to table.col.td_attrs
• Added table.col.th_attrs to override table.thead_th_attrs
• Added table.col.th_wrapper_attrs to override table.th_wrapper_attrs

Checklist

• I added tests that cover my proposed changes.
• I updated the documentation related to my changes (if applicable).

resolves #263

[coveralls]

coverage: 100.0%. remained the same when pulling 7a17a18 on dsrees:override-table-heading-attrs into df23478 on woylie:main.

[woylie]

Thanks, looks good, but the formatter and credo are complaining.