Fix keep-alive behavior

[RFC 2616 section 8.1.1](http://www.w3.org/Protocols/rfc2616/rfc2616-sec8.html#sec8.1) states:

     HTTP implementations SHOULD implement persistent connections.

and [section 14.10](http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.10) defines the "close" connection option.

HTTP/1.0 does not use keep-alive unless the Connection
header is set to "Keep-Alive".