Added new demos to continuous integration

Author: squix78

.travis.yml

@@ -9,8 +9,12 @@ cache:
         - "~/.platformio"
 
 env:
+    - PLATFORMIO_CI_SRC=examples/PlaneSpotterDemo
     - PLATFORMIO_CI_SRC=examples/WeatherStationDemo
+    - PLATFORMIO_CI_SRC=examples/WeatherStationDemoExtended
+    - PLATFORMIO_CI_SRC=examples/WeatherStationDemoExtendedDST
     - PLATFORMIO_CI_SRC=examples/WorldClockDemo
+    - PLATFORMIO_CI_SRC=examples/WundergroundClientPlainDemo
 
 
 install: