Threat control LWRP

Cf. first commit and README changes:

Add a threat_control LWRP, allowing to whitelist/blacklist IPs on CloudFlare
* Stores last action in a node attribute cache, CF API is only called once per day, or if status changes
* IP attribute defaults to current's node IP address
789ee70
Didn't put a date for 0.1.7 in the README, feel free to add one on merge