Status check reports

Now it's possible to get a report on status checks - a list of failures in the given time period.

![report](https://f.cloud.github.com/assets/612643/2308973/ac68acde-a2c8-11e3-9f13-fb8e8c1ed054.png)

![report-form](https://f.cloud.github.com/assets/612643/2308974/ac96f1e8-a2c8-11e3-972e-dbd9027598c8.png)