title: Failed to resolve: com.google.firebase:firebase-core:16.0.1
body: <p>I'm trying to add firebase cloud storage to my app. Below is the app build.gradle. But it says: 
  Failed to resolve: com.google.firebase:firebase-core:16.0.1.
  Why? There is no firebase-core in the dependencies at all.</p>
  
  <pre><code>apply plugin: 'com.android.application'
  
  android {
      compileSdkVersion 27
      defaultConfig {
          applicationId "com.louise.udacity.mydict"
          minSdkVersion 15
          targetSdkVersion 27
          versionCode 1
          versionName "1.0"
          testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
      }
      buildTypes {
          release {
              minifyEnabled false
              proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
          }
      }
  }
  
  dependencies {
      implementation fileTree(dir: 'libs', include: ['*.jar'])
      implementation 'com.android.support:appcompat-v7:27.1.1'
      implementation 'com.android.support.constraint:constraint-layout:1.1.0'
      implementation 'com.google.firebase:firebase-storage:16.0.1'
      implementation 'com.google.firebase:firebase-auth:16.0.1'
      testImplementation 'junit:junit:4.12'
      androidTestImplementation 'com.android.support.test:runner:1.0.2'
      androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.2'
  
      implementation 'com.google.cloud:google-cloud-storage:1.31.0'
      implementation 'com.firebase:firebase-jobdispatcher:0.8.5'
  }
  
  apply plugin: 'com.google.gms.google-services'
  </code></pre>