Update Screenshot.png (was old small size)

Now that retina screens are available, they suggest using a larger
image, the sizing is located on the image, so it is easy to remember for
themes
deregister scripts that Thematic 2.0 adds

This theme doesn't use any of the original themes menu functionality, so
this needs to be removed.
Update Readme

Updated with some 2.0 information and try to push people to the more
complex, but much more impressive responsive base plus theme I use