update gradle version

Author: kumiko.koshiro

lib/build.gradle

@@ -11,16 +11,19 @@ apply plugin: 'com.android.library'
 apply plugin: 'bintray-release'
 
 android {
-    compileSdkVersion 19
-    buildToolsVersion "19.1.0"
+    compileSdkVersion 21
+    buildToolsVersion "21.1.2"
 
     defaultConfig {
         minSdkVersion 18
-        targetSdkVersion 19
+        targetSdkVersion 21
     }
+
     buildTypes {
         release {
-            runProguard false
+            zipAlignEnabled true
+            minifyEnabled false
+            shrinkResources false
             proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
         }
     }