reattach-to-user-namespace is not needed in Tmux >=2.6

[delphinus]

This issue says reattach-to-user-namespace is not needed now. I also confirmed that it is true with tmux 2.7 from homebrew.

# it operates both correctly
terminal-notifier -message hello
osascript -e 'display notification "hello"'

dein.vim/autoload/dein/util.vim

Lines 105 to 115 in 654c56b

	if exists('$TMUX')
	if !executable('reattach-to-user-namespace')
	call dein#util#_error(
	\ 'Please install "reattach-to-user-namespace" command'
	\ . 'to use notification in tmux.')
	return
	endif
	" Use reattach-to-user-namespace in tmux
	let cmd .= 'reattach-to-user-namespace '
	endif

I think this if block should be removed (or should show note for Tmux <2.6).

[Shougo]

OK.