Add Jenkins Summary widget

This widget displays a summary of a specified Jenkins view. It does not display a single block per job, but only displays the jobs that have failed.

When all jobs are green:

![screen shot 2014-12-27 at 20 10 39](https://cloud.githubusercontent.com/assets/304603/5562102/787ce624-8e04-11e4-8c8d-f7d24f643b10.png)

When there are one or more failures:

![screen shot 2014-12-27 at 20 06 39](https://cloud.githubusercontent.com/assets/304603/5562103/838d1ec6-8e04-11e4-9f2d-d3a08f6181bd.png)