Using Arduino IDE version 1.6.5 with the ESP8266 staging version. The IDE board manager reports this version string: 1.6.5-1160-gef26c5f
https://github.com/esp8266/arduino#staging-version-
Upgraded ArduinoJson to 5.0.5 using the IDE library manager. I am sure it works with older versions because I just upgrade to 5.0.5 today.
The WU test program works on an Adafruit Huzzah board though it should work on any ESP8266.