Add Settings api, and xpathCompression setting for Android

Same as last, time, you need to use my fork of wd.js to run the tests...
The above "CamelBackPromise" class, I decided to publish as a standalone npm module: https://github.com/jonahss/camel-back-promise

Do you feel more comfortable requiring it, or just having it pasted in here?

Having it pasted in makes it a little clearer what it does, but I would just as happily move it out.