remove some references to old ES site and old RetroPie github from the README.md
remove some references to old ES site and old RetroPie github from the README.md

tbhova/EmulationStation,joolswills/EmulationStation,tbhova/EmulationStation,joolswills/EmulationStation,zigurana/EmulationStation,joolswills/EmulationStation,asmorgan24/EmulationStation-Marketplace,asmorgan24/EmulationStation-Marketplace,jrassa/EmulationStation,tbhova/EmulationStation,joolswills/EmulationStation,jrassa/EmulationStation,zigurana/EmulationStation,asmorgan24/EmulationStation-Marketplace,jrassa/EmulationStation,zigurana/EmulationStation,asmorgan24/EmulationStation-Marketplace,jrassa/EmulationStation