Detect and Show Warnings about Map Reduce Jobs

This pull requests add the ability to detect issues with a running or complete map reduce job, visually note to users that an something is amiss, and communicate to the user what is going on and how they might resolve the issue.

The intent of this pull request is primarily to make the setup of detecting and reacting to adverse conditions available so that the community can pool their knowledge of common issues that occur in Pig jobs.  Additionally, included are warnings for map reduce jobs that do not write any records and reducer skew which is detected with a somewhat naive formula we hope to improve on going forward.  We also have more conditions/warnings we will be adding in the future.

A map reduce job that is called out due to having warnings:
![screen shot 2014-02-13 at 11 16 03 am](https://f.cloud.github.com/assets/346362/2162190/664b7a3a-94cf-11e3-8cff-a9cf6d060450.png)

Clicking the warning icon next to the map reduce job brings up a modal explaining what what issues were detected:
![screen shot 2014-02-13 at 11 17 13 am](https://f.cloud.github.com/assets/346362/2162204/907608b6-94cf-11e3-8935-cd76bd698043.png)