* Add setNoDelay and getNoDelay to WiFiServer class

* Remote TCP disconnect not detected

Fixes: https://github.com/espressif/arduino-esp32/issues/263

fixes: https://github.com/espressif/arduino-esp32/issues/119

* Rework WiFiClient

Rework WiFiClient to correct error where making a copy of a WiFiClient object resulted in the socket being closed prematurely.

Added loop and select to write to handle/prevent EAGAIN errors.

* Rework WiFiClient to use shared_ptr

Rework changes to utilize shared_ptr rather than manually maintaining reference count. 

Revert changes to write

* Incorporate comments from review

Move WiFiClientSocketHandle and fd() into WiFiClient.cpp

The send call may return EAGAIN. This indicates a recoverable error and a retry should be attempted. The current implementation treats this as a fatal error. Further, the current implementation strips the error code, setting it to 0, which prevents the caller from handling it directly. 
This change utilizes select to verify the socket is available prior to calling send and will retry on an EAGAIN condition.

need close(sockfd) before sockfd = -1, "_connected = false and close socket" means stop() function. (#73)