add cli option to opt out of TeamCityListener

This adds the option to opt out of the built-in `TeamcityListener` and use the regular `ConsoleListener` instead. This is needed because Teamcity can't handle the duplicate reporting when one is using xml output.

For now, you have to pass `--fixie:OptOutTeamcity true` as the `CommandLineParser` forces the arguments to always be pairs, ideally I'd like to be able to pass only `--fixie:OptOutTeamcity` as a flag. I didn't want to make this change now as it makes things a bit more complicated for parsing cli arguments.

@plioi, if you decide to merge this, please let me know when you plan to publish it to nuget, so that I can update our project.

Ah, and thanks for creating this awesome tool. fixie is awesome.