Update build.gradle

Author: slightfoot

android/build.gradle

@@ -21,8 +21,7 @@ allprojects {
 apply plugin: 'com.android.library'
 
 android {
-    compileSdkVersion 28
-    buildToolsVersion '28.0.3'
+    compileSdkVersion 27
 
     defaultConfig {
         testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"