Adding resource usage printing and -z flag to control on demand list in "server pricing"

* Removing Guardfile since we are not using it
* Bumping dependency on joyent-cloud-pricing which contains new resource usage info (RAM, DISK and CPUs in use based on server list)
* ```-z``` flag to ```knife joyent server pricing``` adds listing of on-demand flavors that are in excess of reserve. Without this flag it's not printed for brevity (this list can be large for some).

This should be it really :)  Thanks for fixing previous PR with attributes!