try reuse tooling config from React Native

android/build.gradle

@@ -1,17 +1,22 @@
 apply plugin: 'com.android.library'
 
+def DEFAULT_COMPILE_SDK_VERSION             = 26
+def DEFAULT_BUILD_TOOLS_VERSION             = "26.0.3"
+def DEFAULT_MIN_SDK_VERSION                 = 16
+def DEFAULT_TARGET_SDK_VERSION              = 26
+
 android {
-    compileSdkVersion 26
-    buildToolsVersion '26.0.3'
+    compileSdkVersion rootProject.findProperty('compileSdkVersion') ?: DEFAULT_COMPILE_SDK_VERSION
+    buildToolsVersion rootProject.findProperty('buildToolsVersion') ?: DEFAULT_BUILD_TOOLS_VERSION
 
     defaultConfig {
-        minSdkVersion 16
-        targetSdkVersion 26
+        minSdkVersion rootProject.findProperty('minSdkVersion') ?: DEFAULT_MIN_SDK_VERSION
+        targetSdkVersion rootProject.findProperty('targetSdkVersion') ?: DEFAULT_TARGET_SDK_VERSION
         versionCode 1
         versionName "1.0"
     }
 }
 
 dependencies {
-    compile 'com.facebook.react:react-native:+'
+    implementation 'com.facebook.react:react-native:+'
 }