Fix bug. If bart_api.routes() called with sched=None, then xml is undefined at https://github.com/projectdelphai/bart_api/blob/fe1001f6bf581dff27966c0dd7a035d9bd4a4bcc/bart_api/__init__.py#L80
Merge pull request #2 from rdhyee/master

Bug fix for undefined xml variable when bart_api.routes() called with sched=None