Adding expand/collapse functionality for request headers

You can see this in action here:

http://wpt.jkle.in/details.php?test=130708_HP_5SK&run=1&cached=0

You also might want to add `?w=1` when reviewing, since I made a bunch of whitespace changes.  My editor trims trailing whitespace, and I converted tabs to spaces since the files were mixed but mostly spaces.  This is for issue #58.