Android : Error:Module version com.loopj.android:android-async-http:1.4.3 depends on libraries but is not a library itself

I am trying to apply material theme. After changing com.android.support:appcompat-v7:19.1.0 in build.gradle file to v7:21.0.0.-rc1 or v7:21+, i am getting following error:

Module version com.loopj.android:android-async-http:1.4.3 depends on libraries but is not a library itself

com.loopj.android:android-async-http:1.4.3 dependency is in another build.gradle which is like a project inside main project.

dependencies {
    compile 'com.loopj.android:android-async-http:1.4.3'
}

Update: I changed it to 1.4.4 but now I am getting:

Error:Execution failed for task ':mergeDebugManifests'. Manifest merging failed. See console for more info.

As per this link, I have 'android-L' everywhere, still no luck