Add vim tap-surround plugin; fix tmux msg color.

Add:
	vim/tap-surround/*
		-my vim tap-surround plugin; used to intuitively control surrounding
		elements (eg parentheses, double/single quotes). `:help tap-surround`

	vim/tap-surround/plugin/tap-surround.vim
		-the main plugin script

	vim/tap-surround/doc/(tags, tap-surround.txt)
		-plugin help file, and vim-generated tags for recognition by the
		editor's manual engine.

Mod:
	tmux.conf
		-status bar didn't occupy the full width of my terminal, and, whenever a
		message appeared with a yellow background, would, after "disappearing",
		remain in the unoccupied portion of my screen's lowest row. Changed
		message bg color to default statusline bg, and fg to a suitably
		contrasting green.