Peppy

Added
- added `sample_name` property to samples object.

Fixed
- Initializing Project with `NaN` value instead of `None` in `from_pandas` method

**This version introduced backwards-incompatible changes.**

Changed
- Replaced `attmap` with `MutableMapping` (which removes some attributes)
- Replaced OrderedDict with dict
- Deprecated support for Python versions <= 3.7

_Due to the changes mentioned above, a few functionalities may be disabled. For example, the `name` and `description` project properties can no longer be accessed with `getitem`; use the `getattr` syntax instead_

Added
- Constructor methods: `Project.from_dict`, `Project.from_pandas`, `Project.from_sample_yaml`, `Project.from_pep_config`

Fixed
- incorrect setting of sample and subsample indexes using from_dict function (452)
- clarified debug messages

Added
- `orient` argument to `to_dict` method

Fixed
- The name of the raw subsample object to match the actual name (list). Commit: 442

Changed
- Reduced the number of items returned in the to_dict(extended=True) method to 3, with the name and description now stored in the config key.

Fixed
- A [bug](https://github.com/pepkit/peppy/issues/435) with custom sample ids
- Improved performance for large tables dramatically