Accept `length` parameter from stdin

[joanfont]

[joanfont]

@kaime ping

[kaime]

Hey, @joanfont, person I have never met! Thank you so much for this contribution. Thanks for helping make the world a better place, for you and for me and the entire human race. There are people dying, you knew?

This could be a very nice feature to ship with the 0.2.0 release. But first, let me take a look at the PR. I need to QA it in order to keep this an enterprise-level dick generator.

Bt the way. You should agree to release your code under the terms of the WTFPL. Is that ok with you?

[kaime]

We also need to update the docs. I can do it for you when the PR is ready to be merged.