Basic support for scenario outlines

See issue #26.

The primary shortcoming of this implementation is that it generates scenarios using the outlines at parse-time, which results in the ecukes output being the scenarios rather than the outlines that cucumber proper would print out.

But if you really want scenario outlines, like I did, this is better than nothing! I've got a very young new project [swallow-window.el](https://github.com/pd/swallow-window.el) that I wanted to drive with ecukes features; it's just vastly easier to read the tests than the corresponding ert-style tests.

The ecukes in that project don't currently point at this fork, but you can of course just alter the Makefile to point at the right ecukes bin if you want to see a working example of these scenario outlines.