Names over dict

I figured that it actually don't need an internal dictionary to hold the version numbers, as the only data it hold and deals with is, major, minor, patch and build.

So I went ahead and replaced the dictionary with four under-attributes/names. And also got rid of the get/set item methods, as they are now directly accessible -  of course with a _ in front, since direct access is not really how the API is intended to be used.