title: 'com.android.support:appcompat-v7:27.1.1' conflicts with com.google.android.gms:play-services-maps:15.0.1?
body: <p>I want to use google map, but the dependency (com.google.android.gms:play-services-maps:15.0.1) conflicts with 'com.android.support:appcompat-v7:27.1.1' .. can anyone help?
  here is my gradle file</p>
  
  <pre><code>apply plugin: 'com.android.application'
  
  android {
    compileSdkVersion 27
    defaultConfig {
      applicationId "com.gamecodeschool.mapso"
      minSdkVersion 18
      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-v7:27.1.0'
    implementation 'com.google.android.gms:play-services-maps:15.0.1'
    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'
  }
  </code></pre>
  
  <p>my top-level build file</p>
  
  <pre><code>    // Top-level build file where you can add configuration options common to all sub-projects/modules.
  
  buildscript {
  
      repositories {
         google()
         jcenter()
        }
  dependencies {
      classpath 'com.android.tools.build:gradle:3.1.3'
  
  
      // NOTE: Do not place your application dependencies here; they belong
      // in the individual module build.gradle files
  }
  </code></pre>
  
  <p>}</p>
  
  <pre><code>allprojects {
      repositories {
          google()
          jcenter()
      }
  }
  
  task clean(type: Delete) {
     delete rootProject.buildDir
  }
  </code></pre>