Fixed runtime notice

Author: hason

src/Gitonomy/Git/Commit.php

@@ -257,7 +257,7 @@ public function getTree()
     /**
      * @return Commit
      */
-    public function getLastModification($path)
+    public function getLastModification($path = null)
     {
         if (0 === strpos($path, '/')) {
             $path = StringHelper::substr($path, 1);

src/Gitonomy/Git/Revision.php

@@ -81,7 +81,7 @@ public function getCommitHash()
      *
      * @return DateTime
      */
-    public function getLastModification()
+    public function getLastModification($path = null)
     {
         return $this->getCommit()->getAuthorDate();
     }