fix authenticate method

Author: gnello

README.md

@@ -1,8 +1,8 @@
 # php-mattermost-driver (v3.7.0)
 
-Completed Php Driver to interact with the [Mattermost Web Service API][4].
+Completed Php Driver to interact with the [Mattermost Web Service API][4].  
+Version of the Mattermost server required: 3.7.0
 
-Version of the Mattermost server required: 3.7.0  
 Please read [the api documentation][1] for further information on using this application.
 
 ## Installation
@@ -31,13 +31,7 @@ Read more about how to install and use Composer on your local machine [here][3].
  ]);
 
  $driver = new Driver($container);
- $login = $driver->authenticate();
- 
- if ($login) {
-    echo "SUCCESS!";
- } else {
-    echo "SOMETHING WENT WRONG.";
- }
+ $result = $driver->authenticate();
  ```
 
 ### Check results
@@ -63,7 +57,7 @@ $requestOptions = [
 $result = $driver->getUserModel()->createUser($requestOptions);
 
 //Get a user
-$res = $driver->getUserModel()->getUserByUsername('username');
+$result = $driver->getUserModel()->getUserByUsername('username');
 ```
 
 ### Team data model
@@ -83,4 +77,4 @@ In Development, coming soon!
 [1]: https://api.mattermost.com/
 [2]: http://www.php-fig.org/psr/psr-7/
 [3]: https://getcomposer.org/doc/00-intro.md#installation-linux-unix-osx
-[4]: https://about.mattermost.com/
+[4]: https://about.mattermost.com/

src/Driver.php

@@ -62,7 +62,7 @@ public function __construct(Container $container)
     }
 
     /**
-     * @return bool
+     * @return null|\Psr\Http\Message\ResponseInterface
      */
     public function authenticate()
     {
@@ -75,16 +75,13 @@ public function authenticate()
         /** @var Client $client */
         $client = $this->container['client'];
         $response = $client->post('/users/login', $options);
-        $statusCode = $response->getStatusCode();
 
-        if ($statusCode == 200) {
+        if ($response->getStatusCode() == 200) {
             $token = $response->getHeader('Token')[0];
             $client->setToken($token);
-
-            return true;
         }
 
-        return false;
+        return $response;
     }
 
     /**