Fixed for Issue1297

I'm new to Git; I seem to have messed up this pull request. Anyway, please only merge the following files:
1. src/mixins/canvas_events.mixin.js
2. src/mixins/canvas_gestures.mixin.js

These contain fixes for https://github.com/kangax/fabric.js/issues/1763 (added a longpress event) and partial fix for https://github.com/kangax/fabric.js/issues/1297

For future reference, how do I only include a subset of files in a pull request? I've stuff in my fork of Fabric that I didn't want to include in this PR. So I created a feature branch, reverted it back to a commit that preceded all my commits and then made changes in the two files listed above. What did I do wrong?