I'm first time working with firebase and having a tough time with dependencies issues.
Error:Execution failed for task ':app:processDebugManifest'. > Manifest merger failed : uses-sdk:minSdkVersion 15 cannot be smaller than version 16 declared in library [com.firebaseui:firebase-ui:2.3.0] Suggestion: use tools:overrideLibrary="com.firebase.ui" to force usage