Add a scope `with_location` to Event.
Add Event#location.
Refactor the map_marker partial.
Compact map_marker.js and use Utils.jsonify.
Remove the map_marker partial, which is no longer useful.
TIL: `x ? y` in CoffeeScript is a shorthand for `if x? then x else y`.
Introduce a Location class.
OK, Ruby 2.1 has introduced flonum, so do not expect identity.
Add Event#location= and make location an accessible attribute.

Add long aliases for lat and lng to Location.
Make Event's location accessible from Liquid templates.
Avoid __send__.
Apply a correct fix for the flonum issue.
Merge pull request #518 from knu/refactor-map_marker

Add Event#location and refactor the map_marker partial.