6 remove dup urls

This fixes issue #6. I made it so that when saving an EyeHistory to the db, it first looks for a duplicate that ended in the last 5 min of when the current EyeHistory started. If there is one or more, these get merged together into the current EyeHistory. 

I also added a 1-time script that back populates this change in our db. this can be ran from the terminal of the server (must have virtualenv activated). Run this in staging first against the staging db (make sure #20 is merged and fixed so that staging actually points to the staging db).