Use .streamline.json when running too

Not just registering. Fixes #195.

This means both running files and running the REPL. And I have to say, this finally feels *amazing*.

Before:

```
$ time _coffee example/
real	0m9.887s
user	0m9.043s
sys	0m0.304s
```

After:

```
$ time _coffee example/
real	0m1.091s
user	0m0.992s
sys	0m0.110s
```

(`example/` is some code of ours, not this repo's `examples` directory.)

I especially love the speedup in the REPL! Because the whole point of the REPL is quick experimentation. =)

PTAL @bjouhier. Lemme know if you'd like the implementation to be any different. Thanks!
This `underscored.run` call used to be above the trampoline logic just above this, but that call used to always pass `registerOnly: true`. Now that the call also runs in some cases, I moved it to after the trampoline logic.

Is that cool? Or does this have any negative side effects?