Adds support for integration testing

with aruba and rspec using custom example groups

This prepares code for #35 and #36
Adds custom matchers for multiple in(ex)clude

prepares for #35 and #36
Adds integration tests for help command

This adds integration tests for help command
Uses custom example group for spec/integration dir
Uses custom matcher for multiple in(ex)clude to test output of cli
Uses aruba for running, saving in(out)put, etc...

This tests should work as an example how to write another
integration tests for this CLI tool.
Merge pull request #45 from petrblaho/integration-testing-frame-rev2

Integration testing frame for CLI