mathlib

5f17abcc - fix(tactic/elide): was untested and buggy. Fixed a few issues (#1638)

fix(tactic/elide): was untested and buggy. Fixed a few issues (#1638) * fix(tactic/elide): was untested and buggy. Fixed a few issues * Update tactics.lean * add copyright header * Update src/tactic/elide.lean Co-Authored-By: Rob Lewis <Rob.y.lewis@gmail.com>