_getTranslate(y = 0, x = 0, z = 0){
        if( this.support.transform3d ) return 'translate3d(' + y +', '+ x +', '+ z +')';
        else if( this.support.translate ) return 'translate('+ y +', '+ x +')';
        else return false;
      }
Get translate value, if the browser supports transfrom3d, it will adopt it.
and the same with translate. if browser doesn't support both return false.
@param {Number} y - Value of Y-axis.
@param {Number} x - Value of X-axis.
@param {Number} z - Value of Z-axis.
@return {String|False}