Replace Ubuntu with boot2docker.

Hi!

I was able to replace the Ubuntu VM with boot2docker (related to #17).

This was possible due to two things...
* A recently added *workaround* to allow [shared folders](https://github.com/boot2docker/boot2docker/pull/284). Using this you can mount HOME on boot2docker to allow for that lovely transparent volume usage!
* This [pull request](https://github.com/boot2docker/boot2docker/pull/93) to provide a fixed ip (a.k.a localdocker) between host and guest (which I rebased on the [latest master](https://github.com/cameronmaske/boot2docker/tree/host-only))

This also removed the need for Vagrant (#26) as you can just use Virtual Box to mount the shared folder!

Sadly, there are a few issues...
1. boot2docker ssh requires a password. You need to ssh into boot2docker to mount the shared folder on the host.  My workaround is to prompt the user with `Enter the password 'tcuser' below to mount folders to Docker Virtual Machine`. Unless `docker-osx destroy` is called, this is a one time thing.  There is https://github.com/boot2docker/boot2docker/issues/192 which could be a possible solution.
2.  The shared folder PR isn't yet merged in, and required a custom ISO to be downloaded. Currently hosted an [Dropbox](https://dl.dropboxusercontent.com/u/12014139/boot2docker.iso).
3. The logic too set DOCKER_IP lives with the boot2docker script. My PR removes the ability to re-configure it.
4. You can no longer control the version of docker installed. It relies entirely on the custom ISO mentioned above (v0.9).
5. The previous localdocker ip of `172.16.42.43` doesn't work with the patched boot2docker. I'm not sure why! **Any listings /etc/hosts for localdocker should be removed before installing the above**.


For me, those work around suit my use case of docker.
I think 2 + 3 could possible be improved by vendoring boot2docker script + iso into docker-osx repo.

[Here is a terminal recording to get an idea of performance vs vagrant + ubuntu](http://asciinema.org/a/8457) + proof it works :)  

Interested to hear thoughts around this!