Better threads implementation

Add closable_tcp_acceptor and closable_tcp_stream

Simplify code for accepting incoming requests

Green threads implementation

Simplify code for accepting incoming requests

Green threads implementation

Add closable_tcp_acceptor and closable_tcp_stream

Simplify code for accepting incoming requests

Add closable_tcp_acceptor and closable_tcp_stream

Simplify code for accepting incoming requests
Merge pull request #4 from tomaka/experimental/green-threads

Green thread model