Updates to make Emacs version more compatible

Since this theme has support for color-theme but emacs24 doesn't require this at all, then `color-theme` shouldn't be a requirement for everyone. 

purcell has his version of `tomorrow` that is compatible with both emacs24 and color-theme but it was using a different scheme of colors—likely his personal modifications for his tastes—and so I took his framework and matched it to the colors here.

It looks like @danielfm has been maintaining that part of the tree so maybe he could take a look at this and see what he thinks.

I left in a *lot* of other things that purcell had already added to enhance the mode—such as some of the magit modes and org-mode stuff.