Settings

added the `settings` api, plus implemented the setting for xpath compression.
added docs and tests

will squash once approved of course,

Oh, also had to add to wd.js to get the tests working. If we are ok with my implementation I'll push there. In the meantime you can clone [my fork of wd.js](https://github.com/jonahss/wd).

And then I'm going to go and update the rest of the clients....

(of course I'll squash, once we're through here ;)
I noticed that running my test alone failed, but running the whole suite passed. Not only that, but when it passed, the first call to finding stuff still errored, but didn't fail the suite.

You're right, sleeps are lazy. I'll see if we can do some sort of detection for when the app has loaded...