Use IDE 1.6.9 for Travis CI builds

Author: sandeepmistry

.travis.yml

@@ -1,7 +1,7 @@
 language: generic
 env:
   global:
-    - IDE_VERSION=1.6.8
+    - IDE_VERSION=1.6.9
   matrix:
     - BOARD="arduino:samd:arduino_zero_edbg"
     - BOARD="arduino:samd:mkr1000"
@@ -23,7 +23,6 @@ before_install:
     fi
   - if [[ "$BOARD" =~ "esp8266:esp8266:" ]]; then
       arduino --pref "boardsmanager.additional.urls=http://arduino.esp8266.com/stable/package_esp8266com_index.json" --install-boards esp8266:esp8266;
-      arduino --pref "boardsmanager.additional.urls=" --save-prefs;
       arduino --install-library NTPClient;
       arduino --install-library NTPClient;
     fi