Fix #2352

`precmd` hooks expect the Zsh Line Editor to not be active.
Running these when the ZLE is active can lead to unpredictable results.
See https://github.com/marlonrichert/zsh-autocomplete/issues/180

Fix #2343

Close #2331

Fix #2336

Fix #2339

SHELL is used for execute actions and the preview and default commands.

--phony was renamed to --disabled in d779ff7e

    src/options.go:463:9: undefined: strings.ReplaceAll
    note: module requires Go 1.13make: *** [Makefile:122: target/fzf-linux_amd64] Erro 2

Fix #2256 

Close #2328

Fix https://github.com/junegunn/fzf.vim/issues/1216

- Correct spelling/grammar

This fixes the following errors with Go 1.15:
```
src/options.go:452:69: conversion from untyped int to string yields a string of one rune, not a string of digits (did you mean fmt.Sprint(x)?)
src/options.go:463:33: conversion from untyped int to string yields a string of one rune, not a string of digits (did you mean fmt.Sprint(x)?)
```

This reverts commit e9bc7331.

The change is no longer necessary since 090dee85.

Fix #2161

- `--phony` renamed to `--disabled` for consistency
    - `--no-phony` is now `--enabled`
- Added `enable-search`, `disable-search`, and `toggle-search` actions
  for `--bind`
- Added `--color` options: `query` and `disabled`

Close #2303

Fix #2289

"alt-" with any case-sensitive character is allowed

This is the opposite of "first" (previously known as "top").

zsh sends SIGCONT when running fzf in a pipe in certain cases,
causing mouse mode to become disabled

Fix #2101