Slight timeout tweaks & fix

Adds a new option resetIdleTimeoutOnSend, set to true by default for backwards compatibility with old behavior. You can set this to false in case you only want data receives to reset idleTimeout for your WebSockets (which is probably the most sane value).

The Linux kernel defaults to a TCP retransmission timeout of 15 minutes, meaning that with resetIdleTimeoutOnSend not set to false can postpone the detection of broken sockets by, well 15 minutes. This can be way too long if your idleTimeout is somewhere around 120 seconds.

TLDR; If your idleTimeout is quite short and you have a stable stream of data flowing to the server, you probably want to set resetIdleTimeoutOnSend = false.

This release also fixes a timeout bug in drain event of WebSockets