Add hubot.Robot.react

[mbland]

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PR Summary

Add hubot.Robot.react

Per #360, this implements robot.react as a replacement for the approach from mbland/hubot-slack-reaction-example v1.1.0. Specifically, the ReactionMessage definition will no longer be required in client code, and this:

robot.listen(
  (message) -> message instanceof ReactionMessage
  handleReaction
)

can now become:

robot.react handleReaction

Robot.react can also take optional matcher and options arguments just like the underlying Robot.listen method:

robot.react(
  (message) -> message.type == 'added' && message.reaction == '+1'
  {id: 'my-reaction-matcher'}
  handleReaction
)

NOTE: It was necessary to bump the hubot development dependency to at least v2.16.0, since that is when the Robot.listen method first appeared. I took the liberty of bumping it to the current version by specifying ^2.19.

Related Issues

Follows from the post-merge discussion of #360.

Test strategy

Unit tests to validate the new Robot.react method as part of the existing Adapter and the new Robot.react suites.

cc: @johnagan @DEGoodmanWilson

[coveralls]

Changes Unknown when pulling e7d95c4 on mbland:robot-react into * on slackhq:master*.

[mbland]

FYI, I updated the "Hello, World!" example to use robot.react as described and confirmed that it works.