Draft of output_to_stdout and output_to_stderr matchers
Fix private indentation
Add require
Use print in specs
Introduce separate classes for the two streams
Use one files for all the specs
Add support for regex expectations in output_to_stream matchers
Add support for composing matchers to output_to_stream matchers
Better output for regex cases
DRYing up expected logic
Add behaves like a matcher specs
Add documentation for output_for_stdout and output_to_stderr
Less code same features
Add cukes for output_to_stdout and output_to_stderr
Make the syntax 1.8 compatible
Use print and warn where possible
Improve docs

- Add backticks where needed
- Use correct reference for the stream
- Mention matchers together with regexps
- Reword the description of the feature
Rely on description_of for all the expectations
Make output_to_stream matchers diffable
Add output_to_stream scenarios for composing matchers feature