Adding normalization to osx32, osx64, win32, and win64.

Here are the changes I made to get [Several changes to help with adding 64bit support. #117](https://github.com/mllrsohn/node-webkit-builder/pull/117) ready to (hopefully) be accepted:

 * Change osx to osx32 and osx64, and win to win32 and win64.
 * Since we're working with one platform at a time I'm using detection on architecture to determine which one to use is a string like 'osx' or 'win' is passed.
 * In the case of this being called from node-webkit-builder, the list containing the platforms has already been modified if it contains 'osx' and/or 'win' to contain 'osx32' and 'osx64' and/or 'win32' and 'win64' respectively.
* Tests have been updated and should all be passing.