Don't include app in maven library

[carlbenson]

There is a conflict when you include an AndroidManifest.xml in your library release.

Error:Execution failed for task ':app:processDebugManifest'.
> Manifest merger failed : Attribute application@allowBackup value=(false) from AndroidManifest.xml:20:9-36
  	is also present at [co.metalab.asyncawait:asyncawait:1.0.0] AndroidManifest.xml:12:9-35 value=(true).
  	Suggestion: add 'tools:replace="android:allowBackup"' to <application> element at AndroidManifest.xml:18:5-280:19 to override.