Support IPv6 hostnames

[creationix]

I want to test a custom upstream using cjdns routing with AAAA records on the public DNS.

This doesn't work currently because lit assumes IPv4 hostnames.

tim@t580:~/test$ lit install creationix/weblit
lit version: 3.6.0
luvi version: v2.7.6
command: install creationix/weblit
load config: /home/tim/.litconfig
connecting: wss://lit.xlr8.tech/
fail: [string "bundle:libs/rdb.lua"]:44: EAI_NONAME
stack traceback:
        [C]: in function 'assert'
        [string "bundle:libs/rdb.lua"]:44: in function 'connectRemote'
        [string "bundle:libs/rdb.lua"]:87: in function 'connect'
        [string "bundle:libs/rdb.lua"]:121: in function 'match'
        [string "bundle:libs/calculate-deps.lua"]:72: in function 'addDep'
        [string "bundle:libs/calculate-deps.lua"]:49: in function 'processDeps'
        [string "bundle:libs/calculate-deps.lua"]:92: in function 'calculateDeps'
        [string "bundle:libs/core.lua"]:530: in function 'installList'
        [string "bundle:commands/install.lua"]:12: in function <[string "bundle:commands/install.lua"]:1>
        [string "bundle:main.lua"]:52: in function <[string "bundle:main.lua"]:39>
        [C]: in function 'xpcall'
        [string "bundle:main.lua"]:39: in function <[string "bundle:main.lua"]:31>