Version bump; changelog

Version bump; changelog

Merge branch 'dev'

* dev: (29 commits)
  Adjust license to include contributors
  Minor doc and todo tweaks
  Run unit & integration tests together so that coverage is correct
  Add plenty of TODOs for integration tests
  Add additional unit tests
  Hotfix: don't pluralise a score of -1 point
  Minor: update Travis Slack token
  Additional tests for isValidEvent
  Split up the app & the server; unit & integration tests; adjust docw
  Additional contrib docs
  Lots more feature requests
  Reorganise somet functionality to make it easier to test
  Move getRandomMessage to messages.js; minor cleanups
  Add simple test suite for index.js - incomplete
  Minor: send 500 rather than 403 when server verification value is not set
  Add simple test suite for messages.js
  Workaround jest bug in jsdom/jsdom#2304
  Fix yarn upgrade in travis
  Upgrade yarn in travis
  Minor docs
  ...

Merge branch 'dev'

* dev:
  Add a small selection of random response messages
  Properly fix Slack retry skip!
  Hotfix: different approach to checking the retry headers
  Minor tweaks only
  Lots more docs
  Minor app.json tweaks
  Minor tweaks only
  Add support for Slack on iOS replacing -- with —
  Drop retries to support both Slack & Heroku free dynos
  Allow PORT to be overridden by environment
  Initial commit of basic app
  Additional docs
  Installation instructions + Heroku app.json