Update README with link to Passport-Gowalla.
Update README with link to Passport-Gowalla.

pandeysoni/passport,arover/passport,modulexcite/passport,bartuspan/passport,jameswomack/passport-restify,Rosmina/createAccount,dentrinh/passport,imjerrybao/passport,shubham13jain/passport,DaAwesomeP/passport,mcanthony/passport,Faiz7412/passport,bevacqua/passport,kidaa/passport,ernestopino/passport,mjhea0/passport,wakashige/passport,kolomiichenko/passport,Trult/passport,1602/passport,qitianchan/passport,jaredhanson/passport