Tweak the square root css to look like 1 contiguous piece

I reduced .sqrt-prefix's top property from .1em to .05em

Here are some screenshots at 400% magnification (click on the images so you can see the non-downscaled picture)

Before
![1](https://f.cloud.github.com/assets/47231/212045/8ae38f0a-82cd-11e2-9301-cfc1c4392f24.png)

After
![2](https://f.cloud.github.com/assets/47231/212046/8d42ce78-82cd-11e2-9f54-2246d9b38a5b.png)