Allow app settings config from damperrc

Running multiple instances of the damper is no longer a PITA. You have options!

1. Edit your app's `.commonplace` file with `"port"` and `"host"` fields
2. Edit `~/.damperrc` with a similar object

The `.damperrc` file should look like this:

```js
{
  "/path/to/project": {"port": 8000},
  "~/myprojects/project": {"port": 8001}
}
```

The paths may point to the heart/src directory for the project or the repository's root (either works).

cc @cvan