Describe the bug
I have put my GitHub token for the changelog generator as a variable in my environment as CHANGELOG_GITHUB_TOKEN as stated in the docs, however the output from the generator states the token doesn't exist: :token=>"No token used".

I assume that it is actually in use because I believe I am exceeding the 50 requests per hour limit for unauthenticated requests to GitHub.

To Reproduce

1. With no token provided as an argument to the generator or set in environment variables, run github_changelog_generator. See that verbose output states :token=>"No token used".
2. Run the generator again with a token provided as an argument: github_changelog_generator -t [YOUR_TOKEN_HERE]. See that verbose output states: :token=>"hidden value"
3. Add token to environment variables as CHANGELOG_GITHUB_TOKEN. Run changelog generator and see that verbose output states: :token=>"No token used".

Expected behavior
Assuming the generator is using the token but this isn't reflecting in the verbose output, I would expect the output to return: :token=>"hidden value", as it does when a token is passed in as an argument.

Additional context
N/A