deferred hook

Adding support for a new hook  “deferred” to be called if the message
delivery is getting delayed.
access: for 'any' list, don't process when org_domain not discoverable

and skip ipv4 literals during HELO
geoip: fail gracefully if geoip-lite isn't installed
graph: handle 'sqlite3' not installed gracefully
data.headers: fail gracefull if address-rfc2822 not installed
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
Merge branch 'master' of https://github.com/pedroaxl/Haraka into pedroaxl-master
Implement fixes to deferred hooks and better docs.

Closes #476
Merge branch 'pedroaxl-master'
Merge pull request #554 from msimerson/net_utils

Net utils
Merge pull request #544 from msimerson/access

access: for 'any' domain combined list, don't process when org_domain empty
Merge pull request #555 from msimerson/graph

graph: handle 'sqlite3' not installed gracefully
Merge pull request #556 from msimerson/geoip

geoip: fail gracefully if geoip-lite isn't installed
Merge pull request #557 from msimerson/headers

data.headers: degrade gracefully if address-rfc2822 not installed
connection: fix improper remove_header path
connection: s/transaction.header.add_header/transaction.add_header/