after push on all branches

Check the effect of a GitHub workflow

* add a selenium test for firefox

* add geckodriver and firefox to travis

* install updated

* install updated

* try out suggested webdriver dependency class

* add more resilience

Copyright year was "20014", replaced to "2014"
Fixed the old github.io URL which no longer exist
See https://github.com/WebGoat/WebGoat/issues/321

Fixed a typo in the documentation and added a colon for better readability

The version of Maven is not compatible with the plugin "org.codehaus.mojo:flatten-maven-plugin:1.2.5" used in webgoat-container
```
[INFO] Using 'UTF-8' encoding to copy filtered resources.
[INFO] Using 'UTF-8' encoding to copy filtered properties files.
[INFO] Copying 1 resource
[INFO] Copying 111 resources
[INFO] The encoding used to copy filtered properties files have not been set. This means that the same encoding will be used to copy filtered properties files as when copying other filtered resources. This might not be what you want! Run your build with --debug to see which files might be affected. Read more at https://maven.apache.org/plugins/maven-resources-plugin/examples/filtering-properties-files.html
[INFO] ------------------------------------------------------------------------
[INFO] Reactor Summary:
[INFO] 
[INFO] webgoat-container ................................. FAILURE [ 18.319 s]
...
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 26.001 s
[INFO] Finished at: 2021-02-06T09:37:58+00:00
[INFO] Final Memory: 49M/162M
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal org.codehaus.mojo:flatten-maven-plugin:1.2.5:flatten (flatten) on project webgoat-container: The plugin org.codehaus.mojo:flatten-maven-plugin:1.2.5 requires Maven version 3.2.5 -> [Help 1]
```

- corrected typos/grammar issues
  - restructured sentences for clarity

* Use try with resources instead of try

* Remove unused lesson

* Remove unused fields

* Typo fix

* No need to use thread-safe object

* Use String case in-sensitive equals