adding minSdkVersion (#241)

* adding minSdkVersion

* Update build.gradle

android/build.gradle

@@ -25,6 +25,9 @@ android {
 
     defaultConfig {
         testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
+        // NOTE(jeffmikels): When targetSdkVersion or minSdkVersion is not set or < 4, gradle adds 
+        // additional scary permissions such as WRITE_EXTERNAL_STORAGE and READ_PHONE_STATE.
+        minSdkVersion 16
     }
     lintOptions {
         disable 'InvalidPackage'