Added missing 'machine-man-preview' accept headers

lib/Github/Api/CurrentUser.php

@@ -18,6 +18,8 @@
  */
 class CurrentUser extends AbstractApi
 {
+ use AcceptHeaderTrait;
+
  public function show()
  {
  return $this->get('/user');
@@ -185,23 +187,27 @@ public function subscriptions()
  }
 
  /**
- * @link https://developer.github.com/v3/integrations/#list-installations-for-user
+ * @link https://developer.github.com/v3/apps/installations/#list-app-installations-accessible-to-the-user-access-token
  *
  * @param array $params
  */
  public function installations(array $params = [])
  {
+ $this->acceptHeaderValue = 'application/vnd.github.machine-man-preview+json';
+
  return $this->get('/user/installations', array_merge(['page' => 1], $params));
  }
 
  /**
- * @link https://developer.github.com/v3/integrations/installations/#list-repositories-accessible-to-the-user-for-an-installation
+ * @link https://developer.github.com/v3/apps/installations/#list-repositories-accessible-to-the-user-access-token
  *
  * @param string $installationId the ID of the Installation
  * @param array $params
  */
  public function repositoriesByInstallation($installationId, array $params = [])
  {
+ $this->acceptHeaderValue = 'application/vnd.github.machine-man-preview+json';
+
  return $this->get(sprintf('/user/installations/%s/repositories', $installationId), array_merge(['page' => 1], $params));
  }
 }