Revert "Stop using `__send__` for including modules"
Revert "Stop using `__send__` for including modules"

This reverts commit 2a2d883a1d67a4c29fe6515b0c628f9802186b8e.

`Module#include` only became a public method in the 2.1.x series, as far
as I can tell. Since we're currently targeting 2.x, this needs to be
reverted to use `__send__` so we can include modules outside the module
context.

michaelherold/module_builder,michaelherold/module_builder