Node Version support

[duncanmapes]

I see you have the engine set to >=0.10.0. Is that the intended support, because I am having some issues with v4.x?

[nex3]

I think I looked at which versions supported the narrow slice of Node APIs we're using. What sorts of problems are you running into?

[srawlins]

For what its worth, the exit code tests in test/cli_shared.dart under node, on Linux:

• fail for me with node v0.10.24 (the processes always exit 0 instead of the intended exit code) and
• pass for me with node v7.10.0.

[nex3]

Ah, it does look like process.exitCode was added in v0.11.8. I'll update the version constraint accordingly.