test with other display driver -- do not use unless you are sure you want this -- missing font, slow display updates - travis fix

.travis.yml

@@ -49,6 +49,7 @@ install:
   - ln -s $PWD/libraries/SondeLib /usr/local/share/arduino/libraries/SondeLib
   - arduino --install-library "U8g2"
   - arduino --install-library "MicroNMEA"
+  - arduino --install-library "GFX Library for Arduino"
 script:
   - arduino --board esp32:esp32:t-beam --verify $PWD/RX_FSK/RX_FSK.ino
   - find build