add import bundles to use fewer modules

Previously, the only way to have different sets of imports was to have
different packages. Unfortunately, due to how `use` works, this also
means different module files, creating a bunch of very small modules.

With import bundles, multiple different sets of imports can be defined
in a single module, making for more flexibility.

    use My::Test; # Implies My::Base and requires two modules
    use My::Base 'Test'; # Single module!

Fixes #11
clarify docs on arguments and adding custom args
release v0.005