Bunch of docstrings
Use s/conditional instead of s/either

This gives better error reporting.

Closes #1.
Test allegedly better error reporting

Refs #1.
Disallow empty schemas
Improve intro to docs
Simplify security explanation
Maybe SecureRandom is also okay?
Not a WIP anymore, at least hopefully, soon
Installations must also pick a secretish salt
Be more specific about URL-safe base64 encoding