message: remove unused argument and fix useTransition can not be accessed
diff: @@ -149,7 +149,7 @@ const DEFAULT_OPTIONS = {
  }
  export function initMixin(BScroll) {
  - BScroll.prototype._init = function (el, options) {
  + BScroll.prototype._init = function (options) {
  this._handleOptions(options)
  // init private custom events
  @@ -282,7 +282,7 @@ export function initMixin(BScroll) {
  }
  let me = this
  let isInTransition = false
  - let key = this.useTransition ? 'isInTransition' : 'isAnimating'
  + let key = this.options.useTransition ? 'isInTransition' : 'isAnimating'
  Object.defineProperty(this, key, {
  get() {
  return isInTransition
  