Update build.gradle

Author: iWader

android/build.gradle

@@ -21,7 +21,7 @@ android {
     buildToolsVersion rootProject.hasProperty('buildToolsVersion') ? rootProject.buildToolsVersion : DEFAULT_BUILD_TOOLS_VERSION
 
     defaultConfig {
-        minSdkVersion 16
+        minSdkVersion 21
         targetSdkVersion rootProject.hasProperty('targetSdkVersion') ? rootProject.targetSdkVersion : DEFAULT_TARGET_SDK_VERSION
         versionCode 1
         versionName "1.0"