[Suggestion] Accessing the stream directly

[JshGrn]

Hi, I would be open to submitting a PR for this to add ->stream() to the exportable, this can just return getStream() from ExportableService.php I think...?

Use case is for when we are building csv files on the fly and sending them via email, we do not need to store them to disk and creates additional unrequired steps.

[JshGrn]

#9 initial PR for this

[vitorccs]

@JshGrn I have just released v2.0 which adds importing feature + your requested featured

# will get the content in a stream (content placed in a temporary file)
return (new UsersExport)->stream();

See #12