ITP Take 2

[m9brady]

- Add super().__init__() to OIB child class
- Add __str__ definition to OIB/AWI as example of overriding base class
methods and using py3 f-strings
- Constants in all-caps
- Make use of asterisk-unpacking where possible (e.g. self.poly
creation)
- Use .value rather than [()] notation when extracting data from
h5py.File
- Avoid overriding builtin types (e.g. naming a variable "dict")
- Simplify requirements.yml (add geopandas/descartes. should be
OS-agnostic now)
- Small formatting and grammar changes

[kingjml]

Thanks!