feat(Makefile): move rsync from Vagrantfile to Makefile

Moves rsync from the Vagrantfile to the Makefile, enabling
development to occur on non-local Deis deployments (EC2, Rackspace,
etc.).

TESTING: ensure `make build` works the same way, both for the
main Makefile and the individual component Makefiles. To test for
a remote deployment:

```console
$ DEIS_HOSTS="54.12.21.12 54.13.11.4 55.61.2.4" make build
```

You can also test the `make rsync` target directly.

closes #1020
docs(contrib): fix DEIS_HOSTS example

Previous example was invalid.
chore(Makefile): clean up rsync excludes
Merge pull request #1193 from deis/1020-make_rsync

feat(Makefile): move rsync from Vagrantfile to Makefile