Three Dollar Quill

I mostly thought about other things than Stars Without Number today (remember, that's what this BEM stuff is for), but I did make a few improvements:

• Switched PDF output to Weasyprint, which I think is maintained.
• Removed some of the limitations I initially designed into the Selector class.

With those done, I should only need some light tweaking to be ready to test this stuff out. For now, though, sleep.

Good night.