Make frontpage banner text easier to read

At first glance of the homepage, the banner h1 text which describes gunicorn seems very difficult to read: bright green with crosshatch background, with thin white text.

Removing the font-weight: lighter css tag will revert the h1 font-weight to the 400 default, increasing the readability, of some very critical text.

New style:
![2013121215017zhxp](https://f.cloud.github.com/assets/130111/1738298/d39bd30c-6381-11e3-97b4-0eda39e327bc.png)