Update popup styles to have make lines more readable

Hi,

I have some difficulties to view the differents lines in the popups so I propose this patch for the extension.

Here is a screenshot to see what it looks like with it

![style_update](https://f.cloud.github.com/assets/752030/2320136/a9c0f718-a389-11e3-9497-264c1011da5a.png)


-- Bruno