Path finding tests

The issue with the previous RS was that it was missing `deep-equal` from the
package.json, and mocha turns out to be not so great in some aspects, dying
silently, suppressing require time errors.

Not of all the JavaScript programmers are intimately familiar with every nook
and cranny of the test suite anyway. The fact that there will be some relatively
dark corner that would take a few hours illumination makes little difference.

This is not an addition to ripple-lib, just a test, and frankly I'd doubt even
if it were written in JavaScript it'd be given much careful study.

The C++ guys don't do anything with the tests other than running them, and
occassionaly reporting errors.

These coffee-script files are the only substantive addition to test coverage
since Arthur n co wrote the original tests. Otherwise, porting the tests to
mocha is all that's really been done.

With mocha, the latest version of coffee-script, and on node-js, compilation is
done on the fly, with line/column accurate tracebacks.

There's no need for a gruntfile, watch script or anything.

Stefan said it was OK to write tests in coffee-script, and at the time of
writing these, both he and Brandon agreed it was a suitable use case.

Can we remove all `.c` files from the rippled repository? I know the `new`
keyword, which I hardly use directly anyway, so I definitely don't want to have
to learn about `malloc`

  https://github.com/ripple/rippled/blob/e6e090c542d9a9ce5ebd3146b092c63c7e4cc7ca/src/sophia/db/util.c#L84