Add some basic test cases, and refactor context and namespace code.
Add a release changelog.
Add readme, licence, changelog, and tests to gem build.
Move require_dir from the root namespace to the source loader.
Split context.rb into files per class.
Move root context global from distillery to absinthe top level.
Make context into a plugin, and load it into the injection namespace.

This is likely break plugins which require files, since previously plugins
were loaded into the global namespace.