exit() command

[SeifertDaniel]

The splitbrain\phpcli\CLI::run() method terminates with a exit(0) command. It would be helpful to remove that.

In the case that the script should continue to run or must be terminated regularly (PHPUnit tests), the exit command is not helpful. If you need a hard cut, you can add it in the overload class itself. This makes it unnecessarily difficult for everyone to bypass this termination.