installs md5
adds method for creating the image src for gravatar users
adds user photo to account edit screen
adds link to gravatar.com under user photo
links gravatar photo to show page
adds link to gravatar photo to results view
creates migration to add userphoto column to rides, which will hold the url for the user photo
updates the schema for userphoto column in rides
adds set_photo method to ride model
calls set_photo method when a ride is created or updated
links gravatar photo into the results view for the ride
links gravatar photo into the show view for the ride