Close #1018

Run the command as is in cmd.exe with no parsing and escaping.
Explicity set cmd.SysProcAttr so execCommand does not escape the command.
Technically, the command should be escaped with ^ for special characters,
including ". This allows cmd.exe commands to be chained together.

See https://github.com/neovim/neovim/pull/7343#issuecomment-333350201

This commit also updates quoteEntry to use strings.Replace instead of
strconv.Quote which escapes more than \ and ".

- Use bash for `set -o pipefail`
- Fall back to simpler find command when the original command failed

Related: #1061

Remove code that is no longer relevant after the removal of ncurses
renderer. This commit also fixes background color issue on tcell-based
FullscreenRenderer (Windows).

This fixes foreground color inside preview window when the text has ANSI
attributes except for foreground color.

Close #1046

Close #1046

Similarly to --bind or --color.

--expect used to replace the previously specified keys, and
fzf#wrap({'options': '--expect=f1'}) wouldn't work as expected. It
forced us to come up with some ugly hacks like the following:

https://github.com/junegunn/fzf.vim/blob/13b27c45c8bdf6c3a41376bb83e4895edadf8c7e/autoload/fzf/vim.vim#L1086

Calculate the first row of the score matrix during phase 2

Rework of 656963e0. Makes --ansi processing around 20% faster on plain
strings without ANSI codes.

This reverts commit 656963e0.

Instead of notifying the event coordinator (EventBox) whenever a new
line is arrived, start a background goroutine that periodically does the
task. Atomic.StoreInt32 is much cheaper than mutex synchronization
that happens during EventBox update.

https://github.com/junegunn/fzf/issues/444#issuecomment-321719604

When $ is the leading character in a query, it's probably not meant to
be an anchor.

https://github.com/junegunn/fzf/issues/444#issuecomment-321432803

Close #444

One can escape meta characters in extended-search mode with backslashes.

  Prefixes:
    \'
    \!
    \^

  Suffix:
    \$

  Term separator:
    \<SPACE>

To keep things simple, we are not going to support escaping of escaped
sequences (e.g. \\') for matching them literally.

Since this is a breaking change, we will bump the minor version.

Close #444

It is reported that it can have an unwanted side effect of clearing the
screen on terminal emulators that do not properly support it.

Patch suggested by @arya.

Close #1011