IPv6 issue

[nova0821]

Hello,

Currently, IoT.js is not supported IPv6 because libtuv is not supporting IPv6.
(In libtuv, codes related IPv6 was deleted.)

1. We need to discuss that IoT.js should support IPv6 or not.
2. (Bug) If IPv6 style address is used, the application is not finished. (I will fix it in libtuv side.)

Is there any reason not supporting IPv6 in libtuv? If there isn't, I think we need to support IPv6 because it is vert important for the IoT.

[nova0821]

Bug is fixed with #400.