Cabinets

* Fix issue with performing operations on filepaths containing more than one `.`
* Reduced log level for commonly recurring log messages

* Replace top-level functions `raw` argument with `parser` argument which takes `True`, `False`, or a `Parser` subclass
* `True` for the default `Parser` class for the given file extension
* `False` for no parsing
* `Parser` subclass to parse with that class
* Intelligently pass keyword arguments to `Cabinet`s and `Parser`s
* Added docstrings to top-level functions

- Allows top level functions to accept `kwargs` and passes them down to content methods
- Plain text parser now accepts a custom encoding argument

* Rename built-in plugin modules to avoid standard library conflicts
* Add top-level `set_configuration(protocol, **kwargs)` function
* Fix support for relative paths that include `.`

* Remove protection naming from `_content` methods in `Cabinet`
* Improve README documentation

- Add a plugin system to support additional protocols and extensions
- Remove the `Cabinets` class in favor of importing functions from the package level