Improve test failure summary appearance

[JENKINS-19884](https://issues.jenkins-ci.org/browse/JENKINS-19884): Show more details in the failed test overview.
Before:
![tfs-before](https://f.cloud.github.com/assets/206841/1268859/eae9f43a-2cea-11e3-828d-c3447fd5275c.png)
After:
![tfs-after](https://f.cloud.github.com/assets/206841/1268869/1ecfca86-2ceb-11e3-9b08-8f0206a5de5a.png)