Better makefile

Greatly simplified the build process now that I better understand Godep. Basically boils down to this:

* install `godep`
* set your project GOPATH
* checkout kubernetes to `$GOPATH/github.com/mesosphere/kubernetes`
* `cd kubernetes && make bootstrap install DESTDIR=/where.you.want.the.apps`

@adam-mesos @nqn PTAL
handled by go-deps. will update readme