If global.location.protocol isn't 'http:' or 'https:', use
'http:'. This makes behavior reasonable when the page is
opened directly without using a server.
Make options handling logic match node's `http` module more
closely and let the browser handle all of the relative url
cases itself.
This has a few important advantages:
* Behavior is closer to native `http` modula
* Relative paths in urls are handled properly (fixes#16)
* Code is simpler and more obviously correct
John Hiesey