Update CONTRIBUTING.md
Update CONTRIBUTING.md

Signed-off-by: Kenji Suzuki <78f369cc69f379c1f9c97db1c349e51d90a0293d@gmail.com>

fuel/fuel,yamadatarousan/game,atarun/web,uzura8/flockbird,atarun/web,himaratsu/appbot,atarun/web,wata727/fuel-simplesamlphp-example,ice-inc/sakana,kiro112/deck_cards,notfoundsam/yahooauc,uzura8/flockbird,Darragh-McCarthy/basic-ajax-login,yamadatarousan/game,y-ohgi/fuel_unity,thuraucsy/fuel,notfoundsam/yahooauc,uzura8/flockbird,vano00/blog,notfoundsam/yahooauc,Darragh-McCarthy/angular-ajax-login,vano00/jobs,kenjis/fuelphp1st-2nd-contact-form,atarun/web,notfoundsam/yahooauc,Darragh-McCarthy/angular-ajax-login,Darragh-McCarthy/basic-ajax-login,atarun/web,fjcarreterox/agdata-management,niinoeiichi/de,vano00/jobs,qipa/fuel,niinoeiichi/de,atarun/web,arushishi/gmenu,atarun/web,uzura8/fuel_sample,fjcarreterox/agdata-management,taishikato/Practice-Fuel-PHP,atarun/web,atarun/web,arushishi/gmenu,atarun/web,actcat/sideci_php_sandbox2,uzura8/flockbird,vano00/blog