The first TestNG "native" integration.

The simplest usage:

    import cucumber.api.testng.AbstractTestNGCucumberTests;

    public class RunCukesTest extends AbstractTestNGCucumberTests {
    }

Note: Maybe there should be a more appropriate TestNG reporter for Cucumber.
Changes according to code review
Added TestNG support. Added a HTML escape fuinction. Closes #441, #526