[CI] recover tag name from TRAVIS instead of having it hardcoded (#505)

.travis.yml

@@ -37,6 +37,8 @@ matrix:
         - rm /home/travis/build/1technophile/OpenMQTTGateway/main/User_config.h
         - cp /home/travis/build/1technophile/OpenMQTTGateway/test/Test_config.h /home/travis/build/1technophile/OpenMQTTGateway/main//User_config.h
       script: 
+        - sed -i 's/version_tag/'$TRAVIS_TAG'/g' main/User_config.h
+        - sed -i 's/version_tag/'$TRAVIS_TAG'/g' test/Test_config.h
         - platformio run
         - bash scripts/prepare_deploy.sh
       before_deploy: ls -a