feat(Makefile): add dev-cluster command

### AUTOMATE ALL OF THE THINGS!

Now for working development setup:

``` console
$ export DEISCTL_TUNNEL=172.17.8.100
$ export DEV_REGISTRY=192.168.59.103:5000 # OR YOUR IP
$ make dev-cluster
$ make dev-registry
$ make deploy
```

I think is super useful so I no longer have to set up the vagrant cluster. I'm open to debate on the exact commands being used. I opted not to include `deisctl start platform` because I figured it would mostly be used for development and you would want to deploy from the local registry anyway.
We should add the `discovery-url` target after `dev-cluster` so that's done for you as well. (I was just testing this and forgot to do so.)