redding/mr — pull request #201 by jcredding (2014-04-21 16:39:31+00:00)
Title: Allow passing a block to factory methods

This updates the factory `instance` and `instance_stack` methods
to allow passing a block. It's a common pattern with factories to
`tap` the result. This provides the same functionality without
having to manually to the `tap` call. If no block is provided,
the method behaves as it previously did.

Closes #87

@kellyredding - Ready for review.