A method for processing class_options

Here's a first pass at a method for processing class_options, to try to address https://github.com/wycats/thor/issues/262.  All existing tests pass.  I tried adding a handle_force method to the MyScript class in spec/fixtures/script.thor...but I don't know enough to make a test that passes.  My patch works for me when I actually use it / test it manually.

Thoughts?

Thanks for your help.