Add back nightly build environment

Author: kotl

Diff for: .travis.yml

@@ -9,6 +9,7 @@ addons:
     - g++-4.8
 env:
 - ARDUINO_VERSION=1.6.9 ARDUINO_ESP8266_VERSION=2.3.0 LIB_NEOPIXEL_VERSION=v1.0.5 LIB_GFX_VERSION=v1.1.5 LIB_SSD1306_VERSION=1.1.0 LIB_JSON_VERSION=v5.11.2 ARDUINO_ROOT=${HOME}/arduino-${ARDUINO_VERSION} ARDUINO_ESP8266_ROOT=${ARDUINO_ROOT}/hardware/esp8266com/esp8266 ARDUINO_HOME=${HOME}/Arduino
+- ARDUINO_VERSION=nightly ARDUINO_ESP8266_VERSION=master LIB_NEOPIXEL_VERSION=master LIB_GFX_VERSION=master LIB_SSD1306_VERSION=master LIB_JSON_VERSION=master ARDUINO_ROOT=${HOME}/arduino-${ARDUINO_VERSION} ARDUINO_ESP8266_ROOT=${ARDUINO_ROOT}/hardware/esp8266com/esp8266 ARDUINO_HOME=${HOME}/Arduino
 install:
 - if [ "$CXX" = "g++" ]; then export CXX="g++-4.8" CC="gcc-4.8"; fi
 - ( cd ${HOME} && wget https://downloads.arduino.cc/arduino-${ARDUINO_VERSION}-linux64.tar.xz && tar xf arduino-${ARDUINO_VERSION}-linux64.tar.xz )