Limit autoresponder to "open" action

[bkeepers]

It currently autoresponds on any issue action. It should probably be limited to the opened action. Eventually it should probably be configurable, and allow different templates for each action.

cc https://github.com/bkeepers-inc/botland/issues/3

[bkeepers]

@kytrinyx @lee-dohm: if either of you wanted to dig into this, here is the script, which will need to be modified to check for payload.action == "opened".

There's also not any docs for getting started in the code base, so I'll get those started now. 😁