Make logging format configurable (closes #4)

NOTE: the default format for the "test" environment is without
ansi colors, to be easier on remote terminal sessions

lib/cartodb/server_options.js

@@ -15,7 +15,7 @@ module.exports = function(){
         varnish_host: global.environment.varnish.host,
         varnish_port: global.environment.varnish.port,
         cache_enabled: global.environment.cache_enabled,
-        log_format: '[:date] :req[X-Real-IP] \033[90m:method\033[0m \033[36m:req[Host]:url\033[0m \033[90m:status :response-time ms -> :res[Content-Type]\033[0m'
+        log_format: global.environment.log_format
     };
 
     // Set the cache chanel info to invalidate the cache on the frontend server