Add source map to less files.

services/web/Gruntfile.coffee

@@ -137,9 +137,13 @@ module.exports = (grunt) ->
 
 		less:
 			app:
+				options:
+					sourceMap: true
 				files:
 					"public/stylesheets/style.css": "public/stylesheets/style.less"
 			ol:
+				options:
+					sourceMap: true
 				files:
 					"public/stylesheets/ol-style.css": "public/stylesheets/ol-style.less"