Changed Rhino implementation to evaluate scripts in a context instead of the Rhino shell. Also fixed exception catching with Rhino engine and improved RhinoSpec to test for CommonJS support.
added an Engine implementation based on the javax.script API. Works both under jdk7 (Rhino based) and jdk8 (Nashorn based).
Merge pull request #23 from tgambet/pr-rhino-engine

Changed Rhino implementation to evaluate scripts in a context instead of...
Merge pull request #25 from tgambet/nashorn

Added an Engine implementation based on the javax.script API
Update .travis.yml
Upgrade of Trireme in order to resolve Windows problems
-1 appears to be returned on Windows when things fail via Trireme. Using another value that (hopefully) is unlikely to be returned.