Use @mail_user instead of vmail (fix #31)

.fixtures.yml

 fixtures:
   repositories:
-    "augeas": "git://github.com/camptocamp/puppet-augeas.git"
-    "stdlib": "git://github.com/puppetlabs/puppetlabs-stdlib.git"
+    "augeas": "https://github.com/camptocamp/puppet-augeas.git"
+    "stdlib": "https://github.com/puppetlabs/puppetlabs-stdlib.git"
   symlinks:
     "postfix": "#{source_dir}"

templates/master.cf.redhat.erb

@@ -69,7 +69,7 @@ scache	  unix	-	-	n	-	1	scache
 # Also specify in main.cf: maildrop_destination_recipient_limit=1
 #
 maildrop  unix  -       n       n       -       -       pipe
-  flags=DRhu user=vmail argv=/usr/local/bin/maildrop -d ${recipient}
+  flags=DRhu user=<%= @mail_user %> argv=/usr/local/bin/maildrop -d ${recipient}
 #
 # The Cyrus deliver program has changed incompatibly, multiple times.
 #