Change fileName to filename

Summary: There are lots of callsites to $changeset->getFilename() so it seemed
easier to rename getFileName() to getFilename() even if it includes database
change. Plus I think that getFilename() is better.

Test Plan:
Alter database.
Open revision.

Reviewers: epriestley

Reviewed By: epriestley

CC: aran

Differential Revision: https://secure.phabricator.com/D1437

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

@@ -244,7 +244,7 @@ class DifferentialChangesetViewController extends DifferentialController {
 
     $inlines = array();
     foreach ($lint as $msg) {
-      if ($msg['path'] != $changeset->getFileName()) {
+      if ($msg['path'] != $changeset->getFilename()) {
         continue;
       }
       $inline = new DifferentialInlineComment();