Show caution when translated article might be outdated

* In time :smile: 
![screen shot 2014-10-10 at 6 33 07 am]
(https://cloud.githubusercontent.com/assets/194222/4584613/5cc53e9a-4ffc-11e4-8b04-7c2dc5dc3ef0.png)

* Outdated :worried:
![screen shot 2014-10-10 at 6 33 22 am](https://cloud.githubusercontent.com/assets/194222/4584615/5cc8a7ec-4ffc-11e4-9a56-93bf3b35842a.png)

* Original(does not affect)
![screen shot 2014-10-10 at 6 36 05 am](https://cloud.githubusercontent.com/assets/194222/4584614/5cc6cff8-4ffc-11e4-82d8-31a905c3a9c6.png)
Define constant is better like below:

`OUTDATED_SPAN = 30 * 24 * 60 * 60`