Support building io.js binaries on appveyor and travis

[springmeyer]

To fully drop support for node v0.11.x binaries (#389) we'll need to get io.js builds/binary publishing going on travis and appveyor.

• nvm support for io.js - IO.js, node-forward: should/will NVM support more than node? nvm-sh/nvm#590, or ditch nvm and use nave isaacs/nave@e0b9a96
• Come up with a good approach on appveyor - http://help.appveyor.com/discussions/questions/882-iojs-support

/cc @FeodorFitsner

[am11]

Cross referencing: appveyor/ci#113.

[am11]

AppVeryor support has landed! :)

[Mithgol]

We also have nvm support from nvm-sh/nvm#590.

Some caution is necessary because the binary's name is iojs instead of node.

[springmeyer]

this is now working - no longer building for node v0.11.x and instead targeting node v0.12.x - followups at #404