Washington’s mayor, Adrian Fenty, takes a test spin on one of the city’s new shared bikes.Photo: Matt MartinezIf you want to see what a good bike share system can do for a city, go to Lyon, France. I just returned from a week-long visit, and the bikes were coming and going the minute I stepped out of the door: A man in a suit with groceries from the corner market (it looked like bread, milk, and some flowers). German tourists yakking away while riding along the banks of the Rhone River. Students zipping through the Place Bellecour on their way …