If you've never had one before migraine headaches are no picnic. Between the feeling like somebody's testing a sawmill with part of your skull, profound nausea brought about by something as innocuous as sunlight or the sound of a diesel engine, and vertigo that makes walking to the bathroom to retch a challenge, they're something that many of us would probably not wish on our worst enemies (I know I don't). There are few things that can arrest or lessen the severity of migraines once they start. Mostly, all you can do is get someplace dark and quiet and ride …