Support different filenames for API contracts

[dveljacic]

Hi @mkon,

what do you think about this feature that I've tried to implement?

I found your gem useful, but it would be great if it could use different filenames for contracts, instead of just openapi.yaml that was previously hard-coded, especially in cases where there are different versions of the API specs (contracts).

For backward-compatibility reasons, I've set the default filename to openapi.yaml, but left the possibility for the user to define the name as a second argument.

Hoping to hear your feedback and maybe contribute here.

[mkon]

Hi @dveljacic!

Thanks for the contribution, looks good to me. Let's see if it's green then we are good to go.