Generate the ability to make screenshots from local

[drewbrew]

Description

1. Sort shots.yml by filename for more consistent sorting
2. Add a --base-url argument to the screenshots command so you can regenerate images without merging and deploying
3. Address #242 by adding override_schedule_title to a few speakers' bios

Usage:

# with the site running either via docker or bundle exec jekyll serve:
python bin/process.py screenshots --base-url http://localhost:4000 > shots.yml
shot-scraper multi ./shots.yml

[jefftriplett]

We might want to drop the image updates to avoid stepping on each other for the next PR or two that's coming.

Approving for the process.py though.

[drewbrew]

Sounds good. I'll revert my changes to static/ and then merge