Publish refactoring (#298)

* factoring of the publishing function
* integration of json publishing to MQTT
* receiving and transcode json messages from mqtt
* replace the TRACE runtime condition by a buildtime one so as to decrease program size
* remove retainFlag parameter not necessary for the moment
* Increase the scope of tests for arduino mega and esp32
* Update arduinojson library to 5.13.3
* add macros to choose between simple or json publishing or both
* differentiate build test for ATmega2560
* correct wrong sprintf definition
* change IDE version for continuous integration
* let default warning level in arduino ide
* correct pins for ESP32
* reorganize user_config

lib/Adafruit_TSL2561/.travis.yml

@@ -0,0 +1,27 @@
+language: c
+sudo: false
+
+# Blacklist
+branches:
+  except:
+    - gh-pages
+
+env:
+  global:
+     - PRETTYNAME="Adafruit TSL2561 Arduino Library"
+# Optional, will default to "$TRAVIS_BUILD_DIR/Doxyfile"
+#    - DOXYFILE: $TRAVIS_BUILD_DIR/Doxyfile
+
+before_install:
+   - source <(curl -SLs https://raw.githubusercontent.com/adafruit/travis-ci-arduino/master/install.sh)
+
+install:
+   - arduino --install-library "Adafruit Unified Sensor"
+
+script:
+   - build_main_platforms
+
+# Generate and deploy documentation
+after_success:
+  - source <(curl -SLs  https://raw.githubusercontent.com/adafruit/travis-ci-arduino/master/library_check.sh)
+  - source <(curl -SLs  https://raw.githubusercontent.com/adafruit/travis-ci-arduino/master/doxy_gen_and_deploy.sh)