Allow TestNG Cucumber runner to use composition instead of inheritance

Right now to use the TestNG runner you need to inherit from AbstractTestNGCucumberTests.  I'm working on a large existing project where we have a base test class that does a lot of framework setup.  The only solution I had was to copy AbstractTestNGCucumberTests into my project and modify it to inherit from our base class.

This patch removes the need to inherit from AbstractTestNGCucumberTests.  You can still do so if you want.