Figure out a good way to create/update tests for octoherd scripts

[gr2m]

I could imagine to add a --record [name] flag which would record all requests/responses similar to nock's recording feature.

It would write the request fixtures with sensitive credentials removed into a recordings/[name] folder. We could then add a --replay [name] flag to replay the recording as a means of testing, e.g.

$ octoherd --record add-star script.js gr2m/octoherd-test-add-star
[INFO] requests recorded into test/add-star
$ octoherd --replay add-star script.js
[INFO] replay successful

I think for the sake of simplicity we should allow for only one repository to be recorded

It might also make sense to to introduce commands, such as octoherd run, octoherd record, octoherd replay