Added a .rspec file to enable colour
Got rid of the parameter_type dsl. Let's keep it simple and just define classes. Also created a MinMax module that can be extended to give the min/max validators to multiple parameter types.
Raise an error when trying to define a parameter with an unknown type
Since we got rid of the Type suffix in parameter class names, we no longer need to cut that out later
Added the min_max module that I forgot to commit earlier
Require files explicitly so they always get required in the correct order.
Merge pull request #9 from axsh/refactor-parameter-types

Refactor parameter types