apache/spark — pull request #3774 by zsxwing (2014-12-23 06:58:52+00:00)
Title: Fix the format of running-on-yarn.md

Currently, the format about log4j in running-on-yarn.md is a bit messy.

![running-on-yarn](https://cloud.githubusercontent.com/assets/1000778/5535248/204c4b64-8ab4-11e4-83c3-b4722ea0ad9d.png)