Extend emitGreetings to handle a RegExp (#40)
Extend emitGreetings to handle a RegExp (#40)

Closes #28 

## Why are we doing this?

Cherry picks the implementation of `emitGreetings` from #38 without the dedicated object. implements support for `emitGreetings` to be passed an alternative regular expression to be used to trigger `text.greeting` events.

## Did you document your work?

Yes, the SDK `README` has been updated to reflect the expansion of `emitGreetings` capabilities.

## How can someone test these changes?

* run the chat bot, `npm run dev` and send the bot a greeting, _hi_ or _hello_ for example
* edit the application to  set `emitGreetings` to an alternate regular expression in the `Messenger` object constructor; restart the bot, send messages that match the regular expression and observe that these events are treated as `text.greeting`

## What possible risks or adverse effects are there?

Application developers could trigger problems with malformed regular expressions.

## What are the follow-up tasks?

* decide whether or not to move forward with #38 or some form of it

## Are there any known issues?

None identified.

## Did the test coverage decrease?

No, the new capability is covered.
CondeNast/launch-vehicle-fbm