Allow anonymus access to Differential.

Summary:
Add possibility for not logged in users to browse and see Differential
revisions.

Test Plan:
Set 'differential.anonymous-access' config option to true, log out, you should
be able to browse Differential without logging back in.

Reviewers: epriestley, jungejason

Reviewed By: epriestley

CC: aran, epriestley, mareksapota

Differential Revision: 1044

src/applications/differential/controller/changesetview/DifferentialChangesetViewController.php

@@ -19,6 +19,10 @@
 class DifferentialChangesetViewController extends DifferentialController {
 
 
+  public function shouldRequireLogin() {
+    return !$this->allowsAnonymousAccess();
+  }
+
   public function processRequest() {
     $request = $this->getRequest();