interface@ip parsed in config

[leshow]

closes #51

@muja and @theglossy1 I've added the ability to parse an ip here. still needs a little testing but have a look.

It would support

interfaces:
    - eth0@192.168.0.10

when the config is parsed, we look at the available interfaces and restrict the service to only respond on interfaces where the name and IP matches

[coveralls]

coverage: 72.745% (+0.6%) from 72.096%
when pulling 532b2ef on interfaces_parse_ip
into 606adba on master.