Warn/Failure if unknown configuration option is provided

[mmoayyed]

Thank you for this great tool.

A number of options seem to have changed in the most recent release, 4.1.0, such as ignore_urls. Those that are migrating from older versions to the new are not warned about the change in names/options, and so builds begin to fail without details. If options are changed or renamed, the tool should either issue warnings, or should stop/fail the process with a clear error message.

[gjtorikian]

If you would like to sponsor me I can certainly add this feature.

Until then, there is an UPGRADING guide.