runner: Display statistics of a job

Display basic stats of a job: total number of tests, number of passed
tests, number of UITestFailures, number of other failures and success
rate.

Counters are increased by `runner/run`, therefore hiding a row of the
table doesn't affect the numbers.

Stats are displayed in `index.html` above the results table and below the
header line.

![screenshot](https://f.cloud.github.com/assets/3908828/1002238/4d37fdd8-0a79-11e3-8752-d8b2cfcec9c0.png)