Fix rationale parameter to optional.

index.android.js

     })
   }
 
-  request = (permission, { rationale }) => {
+  request = (permission, options) => {
     const androidPermission = permissionTypes[permission]
 
     if (!androidPermission) {
       )
     }
 
+    let rationale = null
+    if (options != null) {
+      rationale = options.rationale
+    }
+
     return PermissionsAndroid.request(androidPermission, rationale).then(
       result => {
         // PermissionsAndroid.request() to native module resolves to boolean