show help if there is not exactly one argument for info, create, download, add and seed, fix #567
show help if there is not exactly one argument for info, create, download, add and seed, fix #567

feross/webtorrent,joshterrill/webtorrent,webtorrent/webtorrent,yciabaud/webtorrent,jamesliu96/webtorrent,yciabaud/webtorrent,feross/webtorrent,arestov/webtorrent,jamesliu96/webtorrent,rom1504/webtorrent,joshterrill/webtorrent,webtorrent/webtorrent