title: Cannot import any firebase related classes
body: <p>I had to setup my android project new. The old version is not working anymore (IDE is not recognizing or whatever).
  So I decided to copy all classes in a new project.
  But I cannot use any import such as</p>
  
  <pre><code>import com.google.firebase.database.ChildEventListener;
  import com.google.firebase.database.DataSnapshot;
  import com.google.firebase.database.DatabaseError;
  import com.google.firebase.database.DatabaseReference;
  import com.google.firebase.database.FirebaseDatabase;
  </code></pre>
  
  <p>I alway get 'Cannot resolve symbol firebase' message.</p>
  
  <p>Here my Gradle app file</p>
  
  <pre><code>  apply plugin: 'com.android.application'
  
      android {
          compileSdkVersion 24
          buildToolsVersion "23.0.3"
          defaultConfig {
              vectorDrawables.useSupportLibrary = true
              applicationId "tgoa.com.moerder"
              minSdkVersion 16
              targetSdkVersion 24
              versionCode 1
              versionName "1.0"
              testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
          }
          buildTypes {
              release {
                  minifyEnabled false
                  proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
              }
          }
  
      packagingOptions {
          exclude 'META-INF/LICENSE'
          exclude 'META-INF/LICENSE-FIREBASE.txt'
          exclude 'META-INF/NOTICE'
      }
  
      dataBinding {
          enabled = true
      }
      }
  
      dependencies {
          compile fileTree(dir: 'libs', include: ['*.jar'])
          androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2', {
              exclude group: 'com.android.support', module: 'support-annotations'
          })
  
  
      compile 'com.android.support:appcompat-v7:24.2.1'
      compile 'com.android.support:support-v4:24.2.1'
      compile 'com.android.support:percent:24.2.1'
      compile 'com.android.support:design:24.2.1'
      compile 'com.android.support:recyclerview-v7:24.2.1'
      compile 'com.google.firebase:firebase-core:9.8.0'
      compile 'com.google.firebase:firebase-database:9.8.0'
      compile 'com.google.firebase:firebase-auth:9.8.0'
      compile 'com.google.firebase:firebase-messaging:9.8.0'
      compile 'com.google.firebase:firebase-config:9.8.0'
      compile 'com.google.android.gms:play-services-appindexing:9.8.0'
      compile 'com.google.android.gms:play-services-gcm:9.8.0'
      compile 'com.firebase:firebase-client-android:2.5.0'
      testCompile 'junit:junit:4.12'
      provided 'org.projectlombok:lombok:1.16.8'
  
  
  }
  apply plugin: 'com.google.gms.google-services'
  </code></pre>
  
  <p>In the gradle build I have included</p>
  
  <pre><code>dependencies {
      classpath 'com.android.tools.build:gradle:2.2.2'
      classpath 'com.google.gms:google-services:3.0.0'
  </code></pre>
  
  <p>Can anybody help me?</p>