emacs-selectrum 3.1 Incremental narrowing in Emacs

Selectrum is a solution for incremental narrowing in Emacs, replacing Helm, Ivy, and IDO. Its design philosophy is based on choosing the right abstractions and prioritizing consistency and predictability over special-cased improvements for particular cases. As such, Selectrum follows existing Emacs conventions where they exist and are reasonable, and it declines to implement features which have marginal benefit compared to the additional complexity of a new interface.