TS-2405 Change the default for proxy.config.net.sock_option_flag_out to
1, which enables TCP_NODELAY.

Authors: bcall, leif, xiongzongtao
TS-612: build fix for uninitialized variable
Add new secure link example plugin

Add an example plugin demonstrating one method of authorizing URL
access based on a shared secret.

This closes #27.
TS-2542 Turn on caching zero length responses by default