Better handling for not found

[cgansen]

404 should not raise exceptions

For example:

http://locations.weconnectchicago.org/location/tlumu@communityoutreachvolunteers.org

and

An ActionController::RoutingError occurred in location#show:

  Not Found
  app/controllers/application_controller.rb:55:in `not_found'

-------------------------------
Request:
-------------------------------

  * URL       : http://locations.weconnectchicago.org/location/back-of-the-yards-library-4650-s-damen-avenue
  * IP address: 180.76.5.196
  * Parameters: {"action"=>"show", "controller"=>"location", "id"=>"back-of-the-yards-library-4650-s-damen-avenue"}
  * Rails root: /app
  * Timestamp : 2013-02-28 06:20:22 -0600