move MockAdapter into hubot repository

[gr2m]

This is in preparation of #1347. Having the declaration of MockAdapter inside the Hubot repository makes sense anyway, it is fairly simple and we depend on it in our tests, so we should have full control. The main problem is that hubot-mock-adapter does require('hubot/src/adapter') which I don’t think is officially supported, it should be require('hubot').Adapter instead.

If we want to keep a hubot-mock-adapter we should bring it up to date (e.g. it refers src/scripts in the README.md which doesn’t exist) and move it to the hubotio GitHub organization.

In #1347 we want to convert the tests independent of the source files, and the changes in this PR became necessary for the tests to still pass after converting all /src/* files to JavaScript.

[mose]

It looks like it's working fine. I think that package still makes sense to be maintained for plugin authors, and having it revived in hubotio/ sounds good. But I see no problem integrating it in main hubot code in any case.

[gr2m]

Is the module used somewhere else? If we decide to move it to our hubotio org I’d be happy to use that again in the tests with a follow up PR, but would like to merge this first so we can move forward with #1347

[bkeepers]

I think this is fine for now, but agree with @mose that it would be good to have this as an external adapter so others can reuse it. But we can save that for another day.