Testlog alignment

Fixes https://github.com/learningequality/ka-lite/issues/2367 Add ellipsis for overflowing usernames on test log and tabular coach reports. 

![selection_083](https://cloud.githubusercontent.com/assets/1319950/4276859/0d1a4aee-3d09-11e4-8fca-9dc09678c8d9.png)
![selection_082](https://cloud.githubusercontent.com/assets/1319950/4276860/0e0efecc-3d09-11e4-8300-ac9eda9fcbfa.png)