By only using leaf functions

Sort performance increases as the size of each sublist decreases (n in
nlog(n) decreases). Merger is then responsible for merging the sorted
lists in order, and since in most cases we are only interesed in the
matches in the first page on the screen so the overhead in the process
is negligible.

https://golang.org/doc/go1.5

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