Only support LTS and greater releases of node

[rgbkrk]

To use newer features of JavaScript and Node.js that are useful and performant (like native Object.assign, built-in Map), we should stick to more recent versions of Node.

[rgbkrk]

/cc @pseudomuto

[pseudomuto]

Nice!

Might need to remove 0.12 as well

[rgbkrk]

I did it based on the LTS schedule, so even though I don't use 0.12 I left it in.

We can certainly cut 0.12 too though, I'm in favor.

[willingc]

Whatever we ultimately decide re: 0.12, we should probably link to https://github.com/nodesource/distributions to give guidance to those users on slow moving LTS versions of Ubuntu or Fedora.

[rgbkrk]

I find it amusing that the tests are intermittently failing only on 0.12.

I agree with linking to node source's guidance with respect to LTS versions of Ubuntu and Fedora.

[willingc]

Unless @minrk objects, I say remove 0.12 and we can link in the readme to the node guidance re: older versions.

[minrk]

👍 I've been meaning to add 6 for a while, but haven't had time to look at why the tests fail. It seems to be testing-related, as I'm pretty sure I've run CHP on node 6 without issues.