DOC: update docstrings for lookup_*symbol
DOC: update docstrings for lookup_*symbol

alphaBenj/zipline,enigmampc/catalyst,bartosh/zipline,alphaBenj/zipline,humdings/zipline,florentchandelier/zipline,Scapogo/zipline,Scapogo/zipline,bartosh/zipline,quantopian/zipline,magne-max/zipline-ja,magne-max/zipline-ja,enigmampc/catalyst,quantopian/zipline,humdings/zipline,florentchandelier/zipline