minor edits in contributing [ci skip]
minor edits in contributing [ci skip]

tritoanst/ccxt,aiueogawa/ccxt,ccxt/ccxt,thijstriemstra/ccxt,aiueogawa/ccxt,thijstriemstra/ccxt,ccxt/ccxt,ccxt/ccxt,tritoanst/ccxt,tritoanst/ccxt,thijstriemstra/ccxt,aiueogawa/ccxt,tritoanst/ccxt,thijstriemstra/ccxt,ccxt/ccxt,ccxt/ccxt,aiueogawa/ccxt