Accept tags argument in behat command [Feature/Enhancement]

[andyzito]

I think there's a use case to be able to specify Behat tags -- for example, you might have a custom tag that you use to exclude tests that should not be run in Travis.

Ideally, the tags specified in the Travis config would be concatenated with the plugin component tag.

For example, in .travis.yml under script: moodle-plugin-ci behat --tags=~@no-travis results in the command running with --tags=@[component]~@moodle-plugin-ci-ignore.

If the maintainer is open to this feature, I would be happy to work on a pull request.

[polothy]

Yes, I like this idea, open to a PR!