message: modify plugin
diff: @@ -8,6 +8,7 @@ interface PluginsMap<T> {
  }
  interface PluginCtor<T> {
  + static: string
  new (bs: BScroll): T
  }
  export default class BScroll extends EventEmitter {
  @@ -19,7 +20,8 @@ export default class BScroll extends EventEmitter {
  hooks: EventEmitter
  [key: string]: any
  - static plugin<T>(name: string, ctor: PluginCtor<T>) {
  + static use<T>(ctor: PluginCtor<T>) {
  + const name = ctor.name
  if (!this._pluginsMap) {
  this._pluginsMap = {}
  }
  