fix(gestures): remove drag event from config

Removes the `drag` event from the gesture config.

Fixes #1025.

Author: crisbeto

src/lib/core/gestures/MdGestureConfig.ts

@@ -7,7 +7,6 @@ export class MdGestureConfig extends HammerGestureConfig {
 
   /* List of new event names to add to the gesture support list */
   events: string[] = [
-    'drag',
     'dragright',
     'dragleft',
     'longpress',