net_utils: s/stun/vs-stun/

vs-stun:
  works with current versions of node.js
  has a nicer API
  provides more net topology data (we don't need it, but nice to have)
package.json: s/stun/vs-stun/, added redis as optional dep
in_host_list: yummy, lotsa delicious tests

Running tests:  [ 'tests/plugins/rcpt_to.in_host_list.js' ]

rcpt_to.in_host_list.js
 in_host_list - miss
 in_host_list - hit
 in_host_regex - undef
 in_host_regex - miss
 in_host_regex - exact hit
 in_host_regex - re hit
 hook_mail - null sender
 hook_mail - miss
 hook_mail - hit
 hook_mail - hit, regex, exact
 hook_mail - hit, regex, pattern
 hook_rcpt - missing txn
 hook_rcpt - hit list
 hook_rcpt - miss list
 hook_rcpt - hit regex, exact
 hook_rcpt - hit regex, pattern
 hook_rcpt - miss regex, pattern
 hook_rcpt - rcpt miss, relaying to local sender

OK: 33 assertions (117ms)
Merge branch 'net_utils' into host_list