Build support with dependencies for Windows

This PR is my fix for https://github.com/matplotlib/matplotlib/issues/1717 .  I expect I'll get feedback on the following points so I'm going to state them upfront:

1.  "Why include dependencies' source zips/tarballs?"  Simply because there is no canonical way to do this on Windows and it's not for the faint of heart.  I think its worth it -- there are many Python programmers on Windows that could contribute but don't want to deal with the details of nmake and cmake.

2.  "The hack with the symlinks in https://github.com/jbmohler/matplotlib/commit/d6fe8c9192181bb0b940cc169c8ac7b57c3724f9 is a dirty hack."  Yes, I agree.  My better suggestion is at https://github.com/matplotlib/matplotlib/pull/2187#issuecomment-52792452 .  Please vote for that or suggest otherwise.

3.  "Tcl/tk zip files are especially large and you only need the headers."  I think I agree.  I did what I did because I think it's nicer to be able update this merely by plopping in the exact thing downloaded from upstream.

4.  "Now you can't use your own builds of freetype on Windows."  That's true (maybe, kind of) ... many windows devs didn't know how to build it at all before.

There you have it ... my CYA encrusted PR.  :)