Allow configurable Android SDK versions from root project to support newer builds

Author: hjames9

android/build.gradle

@@ -1,12 +1,16 @@
 apply plugin: 'com.android.library'
 
+def DEFAULT_COMPILE_SDK_VERSION = 23
+def DEFAULT_BUILD_TOOLS_VERSION = "23.0.1"
+def DEFAULT_TARGET_SDK_VERSION = 22
+
 android {
-    compileSdkVersion 23
-    buildToolsVersion "23.0.1"
+    compileSdkVersion rootProject.hasProperty('compileSdkVersion') ? rootProject.compileSdkVersion : DEFAULT_COMPILE_SDK_VERSION
+    buildToolsVersion rootProject.hasProperty('buildToolsVersion') ? rootProject.buildToolsVersion : DEFAULT_BUILD_TOOLS_VERSION
 
     defaultConfig {
         minSdkVersion 16
-        targetSdkVersion 22
+        targetSdkVersion rootProject.hasProperty('targetSdkVersion') ? rootProject.targetSdkVersion : DEFAULT_TARGET_SDK_VERSION
         versionCode 1
         versionName "1.0"
     }