A widget to display total number of records.

Here's what it looks like:
![screen shot 2014-09-18 at 12 34 52 pm](https://cloud.githubusercontent.com/assets/98301/4323614/f15328da-3f51-11e4-9a9e-5006f49eca4f.png)

Also fixed a CSS issue -- I think the `margin-top` on `table` was intended to apply to just the Precision/Recall table, but it was also applying to the VCF Table.
So far I've been using arrayOf(React.PropType.object).isRequired, to make it a little bit more explicit.