Add missing word to Readme

Add note to Readme about usage of `%`

Fix bugs in insertion logic

Don't expand aliases

Fix bugs in history search

Increase the default minimum delay

Suppress a warning

Fixes #357.

Make the tests compatible with `zsh` 5.4.2

Remove `_gnu_generic` usage

Fixes #318 and possibly #322.

Fix a deadlock in async completion

Fixes #298.