Extend JodaTime integration

This is not perfect since it currently ignores output writer paramter
and assumes clojure.data.json but it is a significantly better choice than
forcing every clojure.data.json user to use JodaTime.

src/monger/joda_time.clj

@@ -1,6 +1,7 @@
 (ns monger.joda-time
   (:import (org.joda.time DateTime DateTimeZone))
-  (:use [monger.conversion]))
+  (:use [monger.conversion])
+  (:require [clojure.data.json :as json]))
 
 ;;
 ;; API
@@ -10,3 +11,16 @@
   org.joda.time.DateTime
   (to-db-object [^org.joda.time.DateTime input]
     (to-db-object (.toDate input))))
+
+(extend-protocol ConvertFromDBObject
+  java.util.Date
+  (from-db-object [^java.util.Date input keywordize]
+    (org.joda.time.DateTime. input)))
+
+
+(extend-protocol json/Write-JSON
+  org.joda.time.DateTime
+  (write-json [^org.joda.time.DateTime object out escape-unicode?]
+    ;; TODO: use .printTo(Writer) here instead of ignoring
+    ;;       out parameter. MK.
+    (.print (org.joda.time.format.ISODateTimeFormat/dateTime) object)))