Add node .12 and io.js to the CIs

[markelog]

.12 is stable and there is a reports of unstable iojs being more stable then .12.

Yeah, travis and appveyor does support them.

[hzoo]

We can also allow failures if needed

environment:
  matrix:
  - nodejs_version: "0.10"
  - nodejs_version: "0.11"
  allow_failures:
  - nodejs_version: "0.12"
  # io.js
  - nodejs_version: "1.0"

[markelog]

Not sure we need allow_failures or .11 - if something fail and we support it then it shouldn't fail :)

[hzoo]

haha yeah ok

[gustavohenke]

# io.js
  - nodejs_version: "1.0"

This option will blow Travis if Node.js reaches 1.0...

[qfox]

Travis uses nvm internally, all is fine here ;-)