Close #1040

Close #1039

Close #1035

Close #1031

Previously a command like `echo a && echo b` would get transformed into
`echo a && echo b | fzf`, which only pipes the output of the second
command. Adding parentheses around the source command avoids this issue,
and works on both Unix and Windows.

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

Close #1007

Close #1023

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.

Close #1017

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.vim/issues/185

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.