Add ability to easily wrap standard inputs and outputs

[cupakromer]

This idea is not new, see:

• https://gist.github.com/adamstegman/926858
• http://rails-bestpractices.com/questions/1-test-stdin-stdout-in-rspec
• http://stackoverflow.com/questions/11349270/test-output-to-command-line-with-rspec

This may need to be two features: silencing output and allowing testing of inputs / outputs.

Still need to think about the DSL. Thoughts?

[cupakromer]

Take a look at Active Support's Kernel reporting methods https://github.com/rails/rails/blob/master/activesupport/lib/active_support/core_ext/kernel/reporting.rb