grid and meta docstrings

cc @theengineear @etpinard 
Ah I see. I guess I want to communicate that you'll get an exception, it'll be of class `exceptions.PlotlyRequestError`. But, not all `exceptions.PlotlyRequestError` will be because the file already exists. However, all `exceptions.PlotlyRequestError` with `status_code` 400 (`exceptions.PlotlyRequestError.status_code`) will be. Maybe i'm splitting hairs here.