Approx. 50% less memory footprint and 40% improvement in query time

In the best case (all ascii), this reduces the memory footprint by 60%
and the response time by 15% to 20%. In the worst case (every line has
non-ascii characters), 3 to 4% overhead is observed.

Fix #636. Patch suggested by @edi9999.

Fix #183

Close junegunn/fzf.vim#173 and #630

Remove `name` option from `termopen`.

`termopen` no longer accepts a `name` option, instead we should suffix the
command with `;#NAME`.

Patch suggested by Mariusz Atamańczuk

Close #627

To make it consistent with the other commands in fzf.vim

Close #617

Close #607

Close #622

Close #620

Close #615

No guarantee in the order in which files are listed

Related: #616

For consistency and (negligible) performance improvement

Use tmux buffers for sending output to preserve character encoding

Related #616

Close #611

Close #612

[zsh] Re-initialize zle when widgets finish

zle automatically calls zle-line-init when it starts to read a new line. Many
Zsh setups use this hook to set the terminal into application mode, since this
will then allow defining keybinds based on the $terminfo variable (the escape
codes in said variable are only valid in application mode).

However, fzf resets the terminal into raw mode, rendering $terminfo values
invalid once the widget has finished. Accordingly, keyboard bindings defined
via $terminfo won’t work anymore.

This fixes the issue by calling zle-line-init when widgets finish. Care is taken
to not call this widget when it is undefined.

Fixes #279

Close #608

Close #605

zsh: pass through exit code from fzf with fzf-file-widget

This allows to have a custom widget like the following, which would
additionally accept the line, but only in case of entries being
selected:

    fzf-file-widget-with-accept() {
      zle fzf-file-widget
      if [[ "$?" == 0 ]] && (( $#BUFFER )); then
        zle accept-line
      fi
    }
    zle     -N   fzf-file-widget-with-accept
    bindkey '\e^T' fzf-file-widget-with-accept

With this `<C-a>t` will launch fzf, and simulate the pressing of "Enter"
afterwards.