These are TODOs I had from a while back.

> // equals, etc. for Plane?
> // Should ray constructor normalize?
> // Make EllipsoidTangentPlane contain plane?

Nah.

> // Does extent triangulator work over IDL?

Please test this, but if it doesn't work in 2D or Columbus view, write an issue.  It doesn't need to holdup this pull request.

> // Tests for new wrapLongitude.

Please add them.  Even though the polygon tests it indirectly, we want to have specific tests.