[SPARK-7589] [STREAMING] [WEBUI] Make "Input Rate" in the Streaming page...

[SPARK-7589] [STREAMING] [WEBUI] Make "Input Rate" in the Streaming page consistent with other pages

This PR makes "Input Rate" in the Streaming page consistent with Job and Stage pages.

![screen shot 2015-05-12 at 5 03 35 pm](https://cloud.githubusercontent.com/assets/1000778/7601444/f943f8ac-f8ca-11e4-8280-a715d814f434.png)
![screen shot 2015-05-12 at 5 07 25 pm](https://cloud.githubusercontent.com/assets/1000778/7601445/f9571c0c-f8ca-11e4-9b12-9317cb55c002.png)

Author: zsxwing <zsxwing@gmail.com>

Closes #6102 from zsxwing/SPARK-7589 and squashes the following commits:

2745225 [zsxwing] Make "Input Rate" in the Streaming page consistent with other pages