Supplying CLI args "as is"

This is the followup on #374. Unfortunately, the issue I had is not resolved, because the new functionality seems to break when I provide arguments like `--foo`.

```clojure
(deftask run []
(println "Args passed:" *args*))
```

```sh
$ boot [ run --port 8080 ]
java.lang.Thread.run Thread.java: 745
java.util.concurrent.ThreadPoolExecutor$Worker.run ThreadPoolExecutor.java: 617
java.util.concurrent.ThreadPoolExecutor.runWorker ThreadPoolExecutor.java: 1142
java.util.concurrent.FutureTask.run FutureTask.java: 266
...
clojure.core/binding-conveyor-fn/fn core.clj: 2020
boot.core/boot/fn core.clj: 1030
...
boot.core/construct-tasks core.clj: 981
...
boot.core/construct-tasks core.clj: 988
java.lang.IllegalArgumentException: Unknown option: "--port"
clojure.lang.ExceptionInfo: Unknown option: "--port"
file: "/tmp/boot.user3615370981886979666.clj"
line: 25
```

Is this the final behavior? It seems like I would have to continue using hacks just to have this very basic feature.