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
Chef documentation is not helping much here, and the name of this method prompts me to believe it should be called if we _actually update_ the resource / change its state, which is not the case here.
Am I wrong?