Setting up a very simple test suite to check the server and build tasks run across nodejs 4, 5 & 6

[andymantell]

The current test in grunt test doesn't actually test anything apart from that the gruntfile can be parsed without error. It doesn't run the build or start the server. This PR introduces a very simple test suite that does a sanity check on the build output and makes a simple request to the express server to check it is up. It extends the travis config to run the test on nodejs 4, 5 and 6 which should allow you to catch any accidental use of anything too new.

I note that there is a push to convert to gulp - this PR relies on grunt so it will need a little tweak if gulp gets merged first.

[joelanman]

we currently aim to support LTS, so you could just test for 4 and 6 if thats easier

[andymantell]

@joelanman I think given how quick the tests run, it's not too much of a problem to have 5 in there as well? Unless that causes you an issue because it implies support for 5?

[joelanman]

@andymantell hey, really sorry but the gulp stuffs gone in so this will need the tweaks you mentioned - I'm not sure what needs doing?

[andymantell]

No problem, I'll update it and sort it out over the next few days. Shouldn't be too much of an issue

[gemmaleigh]

Closing in favour of #299.