Build on windows

Hi and thanks for this great library. We have been using it in webinos and it works like a charm in Linux, mac and android. The main issue we had was on windows which is a pain to build. This is why I made a branch to include all the required sources, modify them a bit in order to compile using visual studio only and no cgwin staff. 

This PR is far from being able to merge in master, as the most appropriate way would have been to ditch the node-waf script and the old build.gyp file and have a unified solution for all platforms using node-gyp.

Unfortunately I don't have the time to do so, but thought of contributing the windows part, just in case I inspire someone to do the task. I can help if needed.

As for the deps, zlib is copied from node and it is actually feasible to not have the sources here as node-gyp downloads them (you can use <(node_root_dir)/deps/zlib/ for the source files.

libzip-0.11.1 is downloaded from the official site and the modified files have been copied to libzip-0.11.1-modified in order to keep them separated and make it easier to create the appropriate patch.

To build it, just do a 

node-gyp configure build

If you don't have node-gyp, npm install -g node-gyp.

Hope this helps and let me know if you consider my proposal to have a unified way of building in all platforms.