[NonGNU ELPA] Buttercup version 1.26

[ELPA update]

Version 1.26 of package Buttercup has just been released in NonGNU ELPA.
You can now find it in M-x package-list RET.

Buttercup describes itself as:
  Behavior-Driven Emacs Lisp Testing

More at https://elpa.nongnu.org/nongnu/buttercup.html