Command-line utility for ingesting data (and support for building more like it)

Hey, guys!

Here's the indexing tool, wrapped in a nice reusable ruby package. I chose ruby because I'm all about that startup speed, no JVM. I also think the libraries for CLI interaction in Ruby are amongst the best. I've used [this](https://github.com/davetron5000/methadone) and I think it has all the features we'll need. It's far better than main, for example.

This could live in a separate repo, but want to get your thoughts on it first. If we're to have more CLI tools that interact with this, it will be useful to have a skeleton in place so we can build them easily.

I've tried documenting it, so if if you find that the README's lacking in information let me know and I'll fix it.

A heads-up - I've seen weird things when using the SDETools git with this, I've had to change my `$PATH` to give the true git priority over that one. Don't know why exactly, but didn't care enough to investigate.

Cheers,
Alex
Can you anchor these? Some are fairly generic and may trip us up elsewhere in the directory structure. I'm mostly thinking of `html` e.g.

    /pathfinder-cli/results.html
    /pathfinder-cli/html