removing border radius from internal progress bar

Nothing big, I just noticed while loading the progress bar had some border radius inside it. Need to be quick to catch it.

![borderradius](https://cloud.githubusercontent.com/assets/197334/3483139/92043fca-038a-11e4-8ac2-bf3c16e70f4b.png)

The border radius was there for either side, but only when it was full and not for partial loads.

I fixed it by instead removing the border radius and telling the container to hide overflow.