Add comments after travis commands

.travis.yml

@@ -14,14 +14,14 @@ before_install:
   - sudo apt update
 
 install:
-  - sudo apt install maven -y
+  - sudo apt install maven -y # this command is only for demonstration reason. Any Travis virtual machine has maven pre-installed by default.
 
 before_script: 
   - cd project  # enter Maven root directory
   - ls -la
 
 script: 
-  - mvn clean package jacoco:report coveralls:report
+  - mvn clean package jacoco:report coveralls:report # the coveralls:report is required only for the coveralls coverage service 
 
 after_success:
-- bash <(curl -s https://codecov.io/bash) -t 1036eb64-2d96-44c6-b132-0dde4e7dfcca
+- bash <(curl -s https://codecov.io/bash) -t 1036eb64-2d96-44c6-b132-0dde4e7dfcca # replace the 1036eb64-2d96-44c6-b132-0dde4e7dfcca with your repository's token obtained by CodeCov