test: add common and latest stable nodejs versions to `travis.yml
test: add common and latest stable nodejs versions to `travis.yml

Additionally test against iojs v1.8, iojs v2.5, iojs v3.3, nodejs 4.3 (latest lts), nodejs 5.6 (latest stable)

No iojs, or nodejs, test failure is 'acceptable' anymore. All tests must pass.

macedigital/express-xml-bodyparser