add WebAudio pan position
hasEventListenerとremoveEventListenerを追加
Update src/event/eventdispatcher.js
hasEventListener修正
added,removedイベントを送出するように追加
 modified removeEventListener.
Merge pull request #32 from daishihmr/webaudio

add WebAudio pan position
Merge pull request #33 from minimo/develop

EventListener回り追加とadded,removedイベント発行
fix
build
Merge branch 'develop' of github.com:phi1618/tmlib.js into develop
build