Feature request: easier workflow for PDF slides

As far as I know, the current workflow for exporting slides to PDF is as follows (http://stackoverflow.com/a/34168948/2184571):

```
jupyter nbconvert --to slides --post serve /path/to/your/notebook.ipynb
```

Append `?print-pdf` to the URL:

```
http://127.0.0.1:8000/.slides.html?print-pdf
```

Finally, use browser's print dialog to print to a PDF file.

Would it be possible to simplify this? For instance, so that something like this would work:

```
jupyter nbconvert --to pdfslides /path/to/your/notebook.ipynb
```

or

```
jupyter nbconvert --to slides --post pdf /path/to/your/notebook.ipynb
```