Undocumented Change: Node 6

[futagoza]

The changelog does not mention at all that this module now requires Node.js v6

1. Did you forget to add it, or did you think this wasn't required?
2. Why did you set the minimum to Node.js v6?

[tleunen]

Bad move. Since Node v4 is still in LTS. We should definitely support it. And removing support should definitely be a breaking change (which was the case since node 6 was added in v3.0.0 if I recall correctly)

Thank you for creating the PR to add the support of node 4 back.