Don't use keg-only and pouring jargon.

This is unnecessarily confusing to end-users and the "fun" naming doesn't really communicate anything. @mistydemeo and I talked about this.

CC @adamv @mistydemeo @jacknagel @tdsmith @asparagui for thoughts and review.
Here I think we can avoid mentioning keg-only altogether; it would probably be clearer to say "a homebrew-built tcl-tk". That it's keg-only isn't really relevant.