function Gravity(g, life, easing) {
      var _this;
      _this = _Force.call(this, 0, g, life, easing) || this;
      _this.name = "Gravity";
      return _this;
    }
@memberof! Proton#
@augments Proton#Proton.Force
@constructor
@alias Proton.Gravity

@param {Number} g 							Gravity
@param {Number} [life=Infinity] 				this behaviour's life
@param {String} [easing=ease.easeLinear] 	this behaviour's easing

@property {String} name The Behaviour name