Let current user update their location and re-geocode them

Added User#edit view and then the User#update action that allow the curr...ent user to update their location if they choose.  There are no checks to see which user is issuing the edit but only the current user can even see the sidebar, so the link is always present, and always updates the current user, this will probably change in future when profiles are public. (Pencil icon by the location)

I thought about using the HTML5 API but it returns lat/long, when the location field is a string.  I think it will get very confusing to update the two things independently, for the users and for us.

Potentially closes issue #68.  Pending agreement and styling!