title: Dependencies conflict error while adding admob gradle to android app
body: <p>I want to add google admob to one of my android app.
  But it shows dependency conflict error while adding google services ads and firebase ads.</p>
  
  <pre><code>apply plugin: 'com.android.application'
  
  apply plugin: 'kotlin-android'
  
  apply plugin: 'kotlin-android-extensions'
  
  android {
  
      compileSdkVersion 28
      defaultConfig {
  
          applicationId "package name"
          minSdkVersion 21
          targetSdkVersion 28
          versionCode 2
          versionName "2"
          testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
  }
      buildTypes {
  
          release {
  
              minifyEnabled false
              shrinkResources false
              proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
          }
      }
  }
  
      dependencies {
  
          implementation fileTree(dir: 'libs', include: ['*.jar'])
          implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version"
          implementation 'com.android.support:appcompat-v7:28.0.0'
          implementation 'com.android.support.constraint:constraint-layout:1.1.3'
          testImplementation 'junit:junit:4.12'
          androidTestImplementation 'com.android.support.test:runner:1.0.2'
          androidTestImplementation'com.android.support.test.espresso:espressocore:3.0.2'
          implementation 'com.android.volley:volley:1.1.0'
          implementation 'com.android.support:support-v4:28.0.0'
          implementation 'com.android.support:design:28.0.0'
          implementation "org.jetbrains.anko:anko-commons:$anko_version"
          implementation 'com.android.support:cardview-v7:28.0.0'
          implementation 'com.squareup.picasso:picasso:2.71828'
          implementation 'com.facebook.shimmer:shimmer:0.4.0'
          implementation 'com.google.firebase:firebase-core:16.0.7'
          implementation 'com.google.firebase:firebase-messaging:17.3.4'
          implementation 'com.skyfishjy.ripplebackground:library:1.0.1'
          implementation 'com.sasank.roundedhorizontalprogress:roundedhorizontalprogress:1.0.1'
          implementation 'com.google.firebase:firebase-auth:16.2.0'
          implementation 'com.google.android.gms:play-services-auth:16.0.1'
          implementation 'com.tomer:fadingtextview:2.5'
          implementation 'com.google.firebase:firebase-ads:18.0.0'
          implementation 'com.google.android.gms:play-services-ads:18.0.0'
      }
      apply plugin: 'com.google.gms.google-services'
  </code></pre>
  
  <p>any help will be highly appericated</p>