Fix #23 other part.

Simplifying the parsing algorithm.
Allow HTTP/1.1 connections to be closed

 - Added support for replacing headers such as "Connection: Keep-alive" with "Connection: close"
 - Check for header "Connection: close" to determine whether to close the connection
 - Catch disposed exception caused after a connection was closed
Merge pull request #26 from hultqvist/master

Fix #23 other part.