Goodtables-pandas-py

Migrate from `goodtables` to `frictionless` (https://github.com/ezwelty/goodtables-pandas-py/pull/3).

The migration results in the removal of custom support for the `pattern` constraint on non-`string` fields and for `minLength` and `maxLength` constraints on fields other than `string`, `array`, or `object`. `frictionless` considers these situations as invalid field schemas.

- Drop mininum required `goodtables` to 2.2.1 and `datapackage` to 1.9.2 to allow the (deprecated) use of the built-in `pattern` constraint on non-`string` fields (827bf01)

- Add license file (173b1b54dcd2f7980044d766b5ba2ea1c3529ebb).

Initial release.