Meta: Fixed README.md Example

The API_Authenticate example was copied from the test suite.
Replaced the getenv() call with a placeholder string for both
the username and password options.

Author: tflanagan

README.md

@@ -21,8 +21,8 @@ try {
 	));
 
 	$qb->api('API_Authenticate', array(
-		'username' => getenv('username'),
-		'password' => getenv('password')
+		'username' => '****',
+		'password' => '****'
 	));
 
 	$response = $qb->api('API_DoQuery', array(