Add a few useful linguist-based shell utilities.

So I wrote a couple of helper scripts a couple of months ago for using `linguist` in the shell or in a script.
I actually use them quite frequently. So I thought I'd clean them up and see if you felt like merging them.

Pretty straightforward. It does what you probably think it does.
- `language`

(While it could instead be tucked inside the `linguist` executable with a flag, this seems simpler to me.)

Humorously named, but actually materially quite useful, shell scripts which call `language`.
- `speaka`
- `shebangalang`

There's usage and documentation in the comments.

Aside: I considered putting these in a separate gem, but since they have to be kept in sync with `linguist` and there's not really a documented "stable API" per se (not a criticism, doesn't really need one), its honestly just not worth the effort of dependency tracking to put these elsewhere.