azavea/OTM2 — pull request #274 by jwalgran (2013-09-03 19:26:53+00:00)
Title: Modify instance urls to use url_name rather than id

We want to allow linking to instances with urls like http://opentreemap.io/philly rather than http://opentreemap.io/12. I added a unique url_name property to the Instance model that uses a RegexValidator to ensure a url-friendly value. The RegexValidator requires all lowercase letters to avoid confusion, since URLs are case insensitive.