Allow user to ignore class options for command

[snehitgajjar]

There are two scenario where this funcitonality can be useful. 🌈

1. There is a class_option with required: true and some command does not need that class option.
2. There are some class options(required: true) which is used by most of the commands but not necessary for other commands.

[snehitgajjar]

The build for 1.8.7 fails with problems in the webmock gem. As far as I can see, my change didn't cause these. It is erring out on requiring webmock/rspec in this file ./spec/actions/create_file_spec.rb.

[lostapathy]

#583 fixes the webmock dep issue that's causing travis to fail here.

[snehitgajjar]

@rafaelfranca Can you please take a look at it?