Feature/change notification img

通知アイコンを任意のhttp配置のjpg,jpeg,JPG,gif,GIF,png,PNGにできる編集
![a4060f8be3d01196ce75979505e20442](https://f.cloud.github.com/assets/931554/1093374/cb723b0a-169a-11e3-8704-62558e2557e9.png)