Updated TOML and such for Registrator CI.

Changes from CY, and new docs format.

Incorporates the new Travis-based tectonic + weave + Documenter workflow in https://github.com/arnavs/test-tectonic.

This isn't meant for Registrator, so there won't be an associated release of the package.

Let's see if this works...

Small docs tweaks, interface polishing, and bumped the Project.toml version number.

Hopefully that list bit will stop Attobot from complaining.

Interface change for differential operators -- now L̄₁₊, L̄₁₋, L̄₂, L₁₊, L₁₋, L₂ all take extended nodes x̄ instead of interior nodes x.

** Trying this again to see if Attobot doesn't complain. **

Contains the(Reflecting(), Reflecting())-style boundary conditions, types, a few example paragraphs and notebooks (LCP, KFE, HJBE), and the new Unicode methods for working with the operators and basis matrices.

Includes a hotfix the Mixed(), Mixed() case.