Added Config File Support for Rhino Wrapper, solves #704

I wrote a little enhancement to the Rhino wrapper.
It now treats --flags seperately, i.e. keeps it out of the opt=value,opt2=value2-Strings we need to use in rhino right now.

I did this to solve #704, to make jshint-rhino understand the config option.

No further options have been implemented, but now that the "flags"-Object is there, maybe...