Maintenance: Update dependency net-ftp to v0.3.7

Gemfile.lock

@@ -349,7 +349,7 @@ GEM
     mysql2 (0.5.6)
     naught (1.1.0)
     nestful (1.1.4)
-    net-ftp (0.3.6)
+    net-ftp (0.3.7)
       net-protocol
       time
     net-http (0.4.1)