Feature/obfsproxy

You're right. 
As you suggest we could have:

```
"gateway_address": "= pick_gateway('gateway_for_'+name)"
```
and then add the expression
```
try{openvpn.gateway_address} || try{nodes_like_me[:services => 'openvpn']['location.name' => location.name].field('openvpn.gateway_address').shuffle.first} || try{nodes_like_me[:services => 'openvpn'].field('openvpn.gateway_address').shuffle.first}
```
in pick_gateway macro in leap_cli.

I tested it and i think it works. Should i push the changes?