Supported node version

[millette]

Currently, travis is testing node 0.10, 0.12, iojs, etc.

And we're not testing anything beyond node 4.0 but 6.0 is LTS now.

[jo]

Yes, we need to clean up the test matrix. What do you propose?

[millette]

Node 4, 6 and 7 but I haven't tested them yet.

We could keep 0.12 since it's maintained till the end of the year according to https://github.com/nodejs/LTS