Adding mailbox_command parameter
Adding mailbox_transport parameter
Added relay parameters needed for amazon SES
Merge pull request #6 from runephilosof/master

Added relay parameters needed for amazon SES
Merge pull request #5 from andschwa/parameters

Parameters
add needed arguments to config and implement additional rules to allow
configuration of our mailserver
fix forgotten configs
restrict to loopback only for relay-only
make relay and config mutually exlusive, add overlapping parameters to
config
removed argument sender_hostname. It is not a valid postfix config
value, but a parameter in postfix::relay class.