logger: always use JSON to log, don't try to prettify

Winston always pretty-print JSON. Workaround that. We loose the color.
People should use jq if they want to pretty print logs.

lib/logger.js

@@ -5,27 +5,25 @@ var _ = require('lodash'),
     expressWinston = require('express-winston'),
     config  = require('./config');
 
-var transports = [
-  new winston.transports.Console({
-    prettyPrint: false,
-    colorize: true,
-    silent: false,
-    timestamp: true,
-    handleExceptions: true,
-    level: config.get('log:level')
-  })
+var commonLogOptions = {
+  prettyPrint: false,
+  timestamp: true,
+  handleExceptions: true,
+  level: config.get('log:level'),
+  json: true,
+  stringify: function(obj) { return JSON.stringify(obj); }
+},
+    transports = [
+  new winston.transports.Console(_.merge({
+    silent: false
+  }, commonLogOptions))
 ];
 
 if (config.get('log:file')) {
   transports.push(
-    new winston.transports.File({
-      prettyPrint: false,
-      colorize: false,
-      timestamp: true,
-      handleExceptions: true,
-      level: config.get('log:level'),
+    new winston.transports.File(_.merge({
       filename: config.get('log:file')
-    })
+    }, commonLogOptions))
   );
 }