Update ip.rb to use vmrun guestVar to get guest IP

Current code can only retrieve NAT or host-only IPs by polling nat/dhcp settings.
By using vmrun's guestVar command instead it's possible to retrieve IPs in all networking setups.
Forgot to strip the newline on the IP address.
Merge pull request #596 from bruienne/master

Update to vmfusion ip.rb helper to retrieve IPs for bridged networks in addition to NAT and host-only