Cmdkit

This release includes core fixes to the `Configuration` class and a new factory method for automatically loading configuration files and merging them. Also included is functionality to automatically explode and type-coerce a `Namespace` created from environment variables. Finally, an `ApplicationGroup` class makes it simple to create a hierarchical CLI without code duplication.

Application classes with resources can now define `__enter__` and `__exit__` methods. `Application.main` now initializes the application using a `with` statement.

After testing this in a few big projects it seems appropriate to bump to version 1.

This release fixes a bug and adds a new feature.

First, the -v/--version flag behavior from `argparse` is fixed via a patch to its version action class and now the VersionOption class that already existed is caught in the _main_ method and takes the proper action.

Second, the `Application` class's `main` method was made more generalizable. Now, you can define a class-level variable named `exceptions` as a dictionary of exception types with handler functions. These handler functions should take the exception instance as its only argument and return an exit status.