Fixed description bug

[james-baber]

Made this as a fix to this issue https://github.com/oldani/HtmlTestRunner/issues/71

I fixed the getDescription method to default to the doc strings first, otherwise use the method name. I also had to update the default template to use the test_description variable as the default. Since the description is know defined as above. I think this would be a good default behavior because it matches your demo in the readme.

If another outcome is needed the user can just change the template, but at least the test_description variable is now correct

Here is my test

[james-baber]

@oldani let me know if this looks good to you