Several regex fixes and code restructure for better css rewriting and ma...

...ke the </head> replace only affect html

Fix for regular expressions so it really makes sure that it's http(s):// since people could name a folder http on their server (http/myawesomefile.html). Shouldn't affect performance too much.

Also fixes the missing ["']{0,1} rules. Example where old CSS rule wouldn't apply:
url("http://media.onexamination.com/css/framework/fonts/fontawesome-webfont.eot?v=3.2.1");

The code restructure makes it a little faster parsing CSS since it doesn't have to run all the HTML rules.

Making the ROBOTS only affect html is a great idea since some JavaScript contains the </head> tag making it crash the JavaScript with the old code.