Formatting: missing semicolons
Fixed: pinch-zoom maintains center, cross-platform

Pinch-zoom implementation moved from binding to 'gestureend' (iOS only event) to using Touch Events (widely supported by mobile browsers). Changes made in handleEvents() and handlePinchZoom(), and added a simple distance() private function to get the distance between two points (used to get distance between touches for both pinch-zoom and doubletap).

Had to change doubletap to only zoom when the two taps originate from coordinates that are close together to avoid overlap with the pinch-zoom event (was previously getting false positives for double-tapping when quickly pinch-zooming outward).

Fixes #189