Move "responses" out of config.json into a separate file

[mikeboiko]

Is your feature request related to a problem? Please describe.
I like to commit config.json to my git repo in order to be able to re-deploy easily.
The responses values are always updating and showing git repo changes.
It's not a huge deal, but it is a nuisance.

Describe the solution you'd like
Ideally, responses could be taken out of config.json and put into a separate file, responses.json.
This way, I could commit config.json to git, and ignore responses.json

Describe alternatives you've considered
I guess I could run a script that strips out everything except responses in config.json and saves it to a new file.
This wouldn't be the most elegant solution though.

Additional context
Amazing tool btw, keep up the good work!