Update CI (Travis, Shippable) to Node 4.4

[agallant]

Travis and Shippable are still running the quite old Node 0.10 - 4.4 is the current LTS version. I'm working on updating uproxy-lib, but it's worth doing this for the other repos as well.

It should be as simple as changing the version in the .yml config file - with uproxy-lib, the test suite still passes. However, there is a moderately noteworthy message near the top:

Starting with io.js 3 and Node.js 4, building native extensions requires C++11-compatible compiler,
which seems unavailable on this VM. Please read
https://docs.travis-ci.com/user/languages/javascript-with-nodejs#Node.js-v4-(or-io.js-v3)-compiler-requirements.

This suggests that we should either switch to Ubuntu Trusty as base (instead of Precise, which is probably what we're on), or set some other config parameters about the compiler. Doesn't seem blocking, but worth being aware of.

I'll update this issue if I find a clear resolution, and continue working in the uproxy-lib repo. I could check out the other project repos too, but as I'm less familiar with their test suites it may be good for others to pick them up.

[agallant]

Going to mark this as resolved, as it seems the C++11 issue is not problematic - both main uProxy repos are now running on CI w/Node 4.4.