Merge branch 'dev' of github.com:starakaj/pixi.js into dev

* 'dev' of github.com:starakaj/pixi.js:
  Removed an unnecessary check for _touchCount === undefined, since the mixin for interactiveTarget will always set this
  See pixijs#2662 --- Added _touchCount to interactiveTarget.js, and removed an extraneous line in InteractionManager.js
  See pixijs#2662 --- bending to the will of eslint
  Fix issue pixijs#2662 Added a touch counter instead of flag to ensure the correct touch count