Always respect tap_max_distance, not just at the end of the gesture (#406)

Fixes #406

In combination with an increased tap_max_touchtime the current implementation
causes a lot of accidental taps when scrolling back and forth.

This is a very simple fix which tracks the distance during the MOVE event.

**Note: ** I needed a solution _now_, that's why I patched hammer. I'm not expecting this to get pulled, I guess adding `reachedTapMaxDistance` to `Hammer.detection.current` is not very elegant. But it works. I hope this helps understanding #406 and solving it nicely.