Report spec

@jackparmer creating a PR to make adding commentary a bit easier!
Flexibility is good, but we've already defined two ways to grab files from plotly:

````
def foo (file_owner_or_url, file_id=None):
    # if file_id is None, assume the first arg is a url
```

is the signature I think we've been using. It'd probably be cool to stick to that.

https://github.com/plotly/python-api/blob/master/plotly/plotly/plotly.py#L300

https://github.com/plotly/python-api/blob/master/plotly/tools.py#L193

FIDs are great, but we're already in the habit of spitting out plot urls, I sorta feel like that's what will be the simplest to use. Totally up for discussion though.