Server.pm: New DuckDuckGo homepage has a new CSS file.

The new CSS file is static.css (or sxxx.css in production). We need to slurp this in, too.
Server: Only load the CSS file once.

Since /?duckduckhack_css=1 already contains all of the CSS files in the page, we only need to load it once.
Merge pull request #92 from duckduckgo/jag/duckpan-fix

Server.pm: New DuckDuckGo homepage has a new CSS file.