getItem now returns null if item never was set before, README.md cleanup

Author: chun-baoluo

README.md

@@ -143,9 +143,9 @@ We unified our library's methods to bring more efficiency and simplify the usabi
 
 ```javascript
 SInfo.setItem('key1', 'value1', {
-sharedPreferencesName: 'mySharedPrefs',
-keychainService: 'myKeychain',
-encrypt: true});
+    sharedPreferencesName: 'mySharedPrefs',
+    keychainService: 'myKeychain'
+});
 ```
 
 If you used Android's getDefaultSharedPreferences in your project the shared preference's name that you are looking for is: **com.mypackage.MyApp_preferences**. On the other hand if you used iOS's Keychain the default service is: **app** which is our default too.
@@ -180,7 +180,7 @@ SInfo.setItem('key1', 'value1', {
   keychainService: 'myKeychain',
   kSecAccessControl: 'kSecAccessControlTouchIDCurrentSet',
   sharedPreferencesName: 'mySharedPrefs',
-  touchID: true,
+  touchID: true
 });
 ```
 

android/src/main/java/br/com/classapp/RNSensitiveInfo/RNSensitiveInfoModule.java

@@ -161,12 +161,14 @@ public void getItem(String key, ReadableMap options, Promise pm) {
             HashMap strings = options.hasKey("strings") ? options.getMap("strings").toHashMap() : new HashMap();
 
             decryptWithAes(value, showModal, strings, pm, null);
-        } else {
+        } else if (value != null) {
             try {
                 pm.resolve(decrypt(value));
             } catch (Exception e) {
                 pm.reject(e);
             }
+        } else {
+            pm.resolve(value);
         }
     }
 
@@ -252,7 +254,7 @@ private void putExtra(String key, String value, SharedPreferences mSharedPrefere
     }
 
     /**
-     * Generates a new AES key and stores it under the { @code KEY_ALIAS } in the
+     * Generates a new RSA key and stores it under the { @code KEY_ALIAS } in the
      * Android Keystore.
      */
     private void initKeyStore() {