Remove hipchat from README

The README includes a package.json that has `hubot-hipchat` in it. I think this could be confusing for users, if that's not the adapter they are using. I originally thought to just remove that, but that still leaves you with a snippet of dependencies that might not be accurate.

Then I remembered `npm install --save`, which updates package.json with the latest version for you. I think that's a better bet!