fix _fingerprint is set checks for ESP32

see Links2004#633 and Links2004#632

Merge branch 'eio_4_ping_handling'

EIO=4 ping handling Links2004#611

version.py can now create WebSocketsVersion.h

bionic is broken for Arduino IDE 1.6.13 so we keep xenial

travis

code style

Merge pull request Links2004#449 from Links2004/socketio

Socket.IO 2.0.x Support

Merge commit '32dd01b91bbae7f10b0b77ac200e69ea064ed44f'

Merge pull request Links2004#265 from Links2004/esp32

ESP32 support
improved test
sorted examples