`--null` is ambiguous. For completeness' sake, we need both `--read0`
and `--print0`.

`--read0` only makes sense when the input contains multiline entries.
However, fzf currently cannot correctly display multiline entries,
I'm going to make `--read0` an undocumented feature.

Use vi-fetch-history on zsh to get history line

In addition to being simpler, it allows subsequent up/down history
or accept-line-and-down-history widgets to work.
Also allow for find being and alias if alias expansion
after command is enabled.

Since the same can be now achieved with --bind KEY:toggle-sort

Considering HISTSIZE and HISTFILESIZE of bash

Remember the exact string given as the key name so that it's possible to
correctly handle synonyms and print the original string.

by making sure that we're back on shell command-line

Close #266

e.g. fzf --bind "ctrl-m:execute:COMMAND..." --bind ctrl-j:accept

This can be used to avoid parse errors that can happen when the command
contains the closing character. Since the command does not finish at
a certain character, the key binding should be the last one in the
group. Suggested by @tiziano88. (#265)

  e.g. fzf --bind "ctrl-m:execute=COMMAND..." --bind ctrl-j:accept

enter (return), space, tab, btab, esc, up, down, left, right

    execute(...)
    execute[...]
    execute~...~
    execute!...!
    execute@...@
    execute#...#
    execute$...$
    execute%...%
    execute^...^
    execute&...&
    execute*...*
    execute:...:
    execute;...;
    execute/.../
    execute|...|

e.g. fzf --bind "ctrl-m:execute(less {})"
     fzf --bind "ctrl-t:execute[tmux new-window -d 'vim {}']"

This change does have positive effect on startup time of fzf when many
number of options are provided.

    time fzf --query=____ --filter=____ --delimiter=q --prompt=________ \
    --nth=1,2,3,4 --with-nth=1,2,3,4 --toggle-sort=ctrl-r \
    --expect=ctrl-x --tiebreak=index --color=light --bind=ctrl-t:accept \
    --history=/tmp/xxx --history-max=1000 --help

    0m0.013s -> 0m0.008s

:(

- Add `--history` option (e.g. fzf --history ~/.fzf.history)
- Add `--history-max` option for limiting the size of the file (default 1000)
- Add `previous-history` and `next-history` actions for `--bind`
    - CTRL-P and CTRL-N are automatically remapped to these actions when
      `--history` is used

Closes #249, #251

Do not rename terminal buffer

To avoid conflict with other neoterm plugins that manage terminals,
prefer named terminals.

Close #257

Merge branch '121-accept-nil-input' of https://github.com/dullgiulio/fzf into dullgiulio-121-accept-nil-input