Support --label for scheduling lists



Pull request for [Support --label for scheduling lists](https://trello.com/c/z2fDNjku/1833-support-label-for-scheduling-lists).

    
And the original nitpick saying "ugly whitespace" was mainly about having "extraneous whitespace" there. I know we two will disagree on that one, but I can provide quotations from [the holy text](http://legacy.python.org/dev/peps/pep-0008/#whitespace-in-expressions-and-statements):

> No:
> ```python
> x             = 1
> y             = 2
> long_variable = 3
> ```

I think this applies to any "whitespace for aligning purposes".