standardize install and configuration of docker

This makes the default OS Ubuntu 14.04 amd64 and uses a "standard" method of installing and configuring Docker.  This will handle installing Docker as well as setting the default options to be unified across providers.  It also makes for an easier upgrade path as drivers simply need to call `InstallDocker`.
Good point.  Thanks!

On Saturday, December 20, 2014, Nathan LeClaire <notifications@github.com>
wrote:

> In drivers/utils.go
> <https://github.com/docker/machine/pull/125#discussion-diff-22143363>:
>
> > @@ -43,3 +46,109 @@ func PublicKeyExists() (bool, error) {
> >  	}
> >  	return false, err
> >  }
> > +
> > +func InstallDocker(driver Driver) error {
>
> Nitpick: I'd call the variable which gets passed to this function d
> instead of driver. It's idiomatic in this codebase to do so and IMO driver
> looks too much like drivers when scanning code quickly.
>
> —
> Reply to this email directly or view it on GitHub
> <https://github.com/docker/machine/pull/125/files#r22143363>.
>