Indentation for readability
Remove dead code: Options class
Remove dead code: Command.assign_cmd?()
Pulled #keys methods in InstanceAbleCommand module
Refactored: Keys, Not compatible commands, help

Outsources the creating of not-compatible commands method, keys method
and help method into superclass creation methods
Refactored: Compatibility checking

This adds a method to the Array class for checking if members of another
array are included in itself.

Based on that we try to find noncompatible commands. If there are any
noncompatible commands the evaluation returns true, so re must return
false and the other way round.
Refactored and shortened #try_precommands
Refactored: #ensure_unique_commands!
Refactored: Expected attr count meth generation on the fly
Removed dead code from InstanceAbleCommand, added comment
Merge branch 'refactor'