List status codes by type (#24)

* method for listing codes by type
* specify type
* include type description
* optimize slow code
* refactor methods with high branch size
* add regex to throw error if type entered is wrong
* fix bug in grouping
* separate code type constant into file
* refactor tests for system exits
* remove redundant code
* add more test coverage
* add rspec matchers to test for actual status code

* bump version

Hotfix for bundler runtime error