fix stopBackgroundTask not called from timer when executed in background

In my tests, adding the "android-minSdkVersion" to config.xml doesn't solve the issue, but using `-- --minSdkVersion=15` in the command fixes it.

added bower

Uses current flavor app id

Currently the plugin pulls the `PACKAGE_NAME`, early on in the build process. After working with Android product flavors where I am building different APKs with different applicationIds (com.test.app.alpha, com.test.app.beta, com.test.app) the permission still sticks with the core package name. These permission requests then conflict with each other when having multiple APKs on the same device, and can even stop the app from being downloaded from the Play Store if the user has an another app on the device with the same permissions.

By using `{applicationId}` it will grab the current App's application ID later on so the current ID is used instead.

Make sure the  object exists in the notification.

Issue #274: Callbacks for actions buttons

Pimp my readme

Resolved conflict with phonegap/phonegap-plugin-push

Mentioning that the unregister method also cleans up event handlers on the docs.

Fixed a typo in README.md