get versions from rootProject

Author: alikazemkhanloo

android/app/build.gradle

@@ -1,11 +1,15 @@
 apply plugin: "com.android.library"
 
+def safeExtGet(prop, fallback) {
+    rootProject.ext.has(prop) ? rootProject.ext.get(prop) : fallback
+}
+
 android {
-    compileSdkVersion 23
-    buildToolsVersion "23.0.1"
+    compileSdkVersion  safeExtGet('compileSdkVersion', 23)
+    buildToolsVersion  safeExtGet('buildToolsVersion', "23.0.1")
     defaultConfig {
         minSdkVersion 16
-        targetSdkVersion 22
+        targetSdkVersion safeExtGet('targetSdkVersion', 22) 
         versionCode 1
         versionName "1.0"
     }