Replace IPC

This pull-request replaces the HTTP channel with regular stdout/stdin communication. This has various advantages:

- No potential security issues anymore because no ports are exposed
- It's faster (tests are actually running twice as fast)

It changes the API and thus requires a major version bump:

- `Phantom.prototype.port` has been removed
- `Phantom.prototype.secret` has been removed
- `config.minPort` has been removed
- `config.maxPort` has been removed

The current implementation requires [a fix in another library](https://github.com/nisaacson/linerstream/pull/4) (pull-request pending). That's why the `package.json` has a dependency to the github pull-request repository.

This change may conflict with existing code if PhantomJS' `stdout` is used.