fix rspec deprecation warnings
no need for separate in_data parameter
remove unneeded ensure

- output and error are already defaulted
Merge pull request #17 from kbrock/fix_rspec_warnings

fix rspec deprecation warnings
Merge pull request #18 from kbrock/remove_in_data_parameter

no need for separate in_data parameter
Single letter parameters default to short form

- CommandLineBuilder now converts parameters with a
single letter into a short parameter (e.g.: -f)
- Added CHANGELOG.md for communicating changes