use hubot-mockadapter instead of hubot-mock-adapter

[gasolin]

I ported hubot-mock-adapter to hubot-mockadapter (plain JS), add some missing mocks like emote function, so we can get more test coverage from tests

I've done the related work on https://github.com/gasolin/webbybot

gasolin/webbybot@845830f

with preference to do the following work directly on ES6 based hubot instead of coffee version #1138

[bkeepers]

The list of hubot adapters in the hubot documentation is being replaced with a link to a GitHub topic search. Add the hubot-adapter topic to your repository on GitHub to include it in this list.

/cc #1320