swipeLeft = function swipeLeft(selector, xOffset, speed) {
  /**
   * we can't use default values for function parameter here because this would
   * break the ability to chain the command with an element if reverse is used
   */
  xOffset = typeof xOffset === 'number' ? xOffset : 100;
  speed = typeof speed === 'number' ? speed : 100;

  /**
   * make sure xoffset is positive so we scroll right
   */
  xOffset = xOffset > 0 ? xOffset * -1 : xOffset;

  return this.pause(100).swipe(selector, xOffset, 0, speed);
}
Perform a swipe left on an element.

@alias browser.swipeLeft
@param {String} selector  element to swipe on
@param {Number=} xoffset    x offset of swipe gesture (in pixels or relative units)
@param {Number} speed     time (in seconds) to spend performing the swipe
@uses mobile/flick
@type mobile