fix small typo add requirements.txt

[jgraham909]

Thanks for sharing, I've been meaning to look at beautiful soup for a while.

Looks like there is a typo on line 50 of collect_texts.py

Added requirements.txt to capture dependencies to easily install via pip install -r requirements.txt especially convenient if using conda environments to avoid cluttering main python env.

This also required liblept5 and firefox-geckodriver installed via apt on ubuntu before anything would run. Maybe I'll try to document the full set via a Dockerfile as I'm sure there are other dependencies I already had installed.

There appear to be other issues I'm struggling through, not sure if user error, documentation, or something other. I'll try to grok things a bit better so I can articulate the other issues and either create issues or PRs.

[billfitzgerald]

These are both great additions.

And yeah, the documentation definitely needs improvement.

Also: Huge +1 for a Dockerfile - that would be amazing.