[DEBUG] ipv4 parsing

If user happen to specify ipv4 in config file with less than three
digit at the last 8bit address space, address parsing not work
correctly.
Make it more readable and remove unused codes
Merge pull request #8 from kyuhojeong/ipv4_split

[DEBUG] ipv4 parsing
config: save local uid.

So peer can know that we are the same machine.
Support user defined ip addresses.

User can define peer ip in json file.
Use '-p ip_config.json' to load the ip configuration.
Format of ip_config.json (An json array):

[
        {
            "uid": "54f2b14f80e5374f8af7ad1b4838145ea7eaaf57",
            "ipv4": "172.31.0.101",
            "desc": "Linux VM"
        }
]
fixup bug when assign ip address.
Replace extraneous eval with getattr

This changes the format of the configuration file slightly.
Merge pull request #9 from kangjianbin/master

Save local uid and add an option to load peer uid<->ip mapping configuration