update readme sample

README.md

@@ -384,19 +384,33 @@ This library ships with a `CredentialsManager` class to easily store and retriev
 
 ### Usage
 1. **Instantiate the manager**
+You'll need an `AuthenticationAPIClient` instance used to renew the credentials when they expire and a `Storage`. The Storage implementation is up to you. We provide a `SharedPreferencesStorage` that uses `SharedPreferences` to create a file in the application's directory with Context.MODE_PRIVATE mode. This implementation is thread safe and can either be obtained through a Singleton like method or be created every time it's needed.
 
 ```java
-AuthenticationAPIClient authClient = //create auth client
-Storage storage = //create new storage
-CredentialsManager manager = new CredentialsManager(authClient, storage);
+AuthenticationAPIClient authentication = new AuthenticationAPIClient(account);
+Storage storage = new SharedPreferencesStorage(this);
+CredentialsManager manager = new CredentialsManager(authentication, storage);
 ```
 
 2. **Save credentials**
-The credentials **must have** `expires_in` and at least an `access_token` or `id_token` value. If one of the values is missing when trying to set the credentials, the method will throw a `CredentialsManagerException`. 
+The credentials to save **must have** `expires_in` and at least an `access_token` or `id_token` value. If one of the values is missing when trying to set the credentials, the method will throw a `CredentialsManagerException`. If you want the manager to successfully renew the credentials when expired you must also request the `offline_access` scope when logging in in order to receive a `refresh_token` value along with the rest of the tokens. i.e. Logging in with a database connection and saving the credentials:
 
 ```java
-Credentials credentials = //login to Auth0, i.e. by using the authClient
-manager.setCredentials(credentials);
+authentication
+    .login("info@auth0.com", "a secret password", "my-database-connection")
+    .setScope("openid offline_access")
+    .start(new BaseCallback<Credentials>() {
+        @Override
+        public void onSuccess(Credentials credentials) {
+            //Save the credentials
+            manager.saveCredentials(credentials);
+        }
+
+        @Override
+        public void onFailure(AuthenticationException error) {
+            //Error!
+        }
+    });
 ```
 
 3. **Retrieve credentials**
@@ -405,19 +419,15 @@ manager.setCredentials(credentials);
 ```java
 manager.getCredentials(new BaseCallback<Credentials, CredentialsManagerException>(){
    public void onSuccess(Credentials credentials){
-      //success
+      //Use the Credentials
    }
 
     public void onFailure(CredentialsManagerException error){
-      //error
+      //Error!
    }
 });
 ```
 
-### Customize the Storage
-
-The storage implementation is up to you. We provide a `SharedPreferencesStorage` that uses `SharedPreferences` to create a file in the application directory with Context.MODE_PRIVATE mode.
-
 
 ## FAQ
 

auth0/src/main/java/com/auth0/android/authentication/storage/Storage.java

@@ -4,7 +4,8 @@
 import android.support.annotation.Nullable;
 
 /**
- * Represents a Storage of generic key-value data.
+ * Represents a Storage of key-value data.
+ * Supported classes are String, Long and Integer.
  */
 @SuppressWarnings("WeakerAccess")
 public interface Storage {