Build a basic calendar view

Summary:
This is a very small step toward building a Status and possibly an Oncall tool.
Build a calendar view which renders months.

Much of my hesitance to bang these tools out is that dealing with
dates/calendaring is basically horrible, so I'm trying to ease into it.

This calendar is locale-aware and all that jazz.

Test Plan:
  - See:
https://secure.phabricator.com/file/view/PHID-FILE-c07a9c663a7d040d2529/
  - Verified that months have the right number of days, today is the right day
of the week, months begin on the day after previous months end on, etc.

Reviewed By: aran
Reviewers: jungejason, tuomaspelkonen, aran
Commenters: cwbeck, jungejason
CC: blair, aran, epriestley, cwbeck, jungejason
Differential Revision: 791

src/aphront/default/configuration/AphrontDefaultApplicationConfiguration.php

@@ -356,6 +356,10 @@ class AphrontDefaultApplicationConfiguration
         'preview/$' => 'PhrictionDocumentPreviewController',
         'diff/(?P<id>\d+)/$' => 'PhrictionDiffController',
       ),
+
+      '/calendar/' => array(
+        '$' => 'PhabricatorCalendarBrowseController',
+      ),
     );
   }