Update for Android Studio 3.1

app/build.gradle

@@ -1,11 +1,7 @@
-import com.android.builder.model.ProductFlavor
-import org.apache.tools.ant.taskdefs.condition.Os
-
 apply plugin: 'com.android.application'
 
 android {
     compileSdkVersion 27
-    buildToolsVersion '27.0.3'
 
     defaultConfig {
         minSdkVersion 16