Allow "api" and so-called sections in domains, subdomains

Before this change, baseUrl would not be computed correctly if the location.origin has a so-called section like "api" in it. For example, we're hosting ngdocs at http://cdn-angular-api.example.com/ngdocs. Because the subdomain has "api" in it, the baseUrl variable would be set to "http://cdn-angular-" and all the JavaScript and CSS resources for ngdocs wouldn't load. With this change in how baseUrl is determined, any string that is a "section" in the RegEx immediately above the change can now be used in a domain or subdomain. Without this fix, if any string that appears in <%= sections %> also appears in the domain or subdomains, baseUrl will not be correct.