Fixed issue with mixed path separators with s3cmd get --recursive on Windows

s3cmd get fails on Windows when it needs to create a directory. The s3 path is not localized to local path separators, so the s3 portion of the path is not identified as a directory. 

This issue results in error 183, discussed [here](http://sourceforge.net/p/s3tools/mailman/s3tools-bugs/thread/CAP6d-HXG08_5gfLYAUs6SkGx%2BeszC3GQ2wwOnrHJOk4RQ7wtnw@mail.gmail.com/) and [here](http://www.region3dfg.org/comp/AWS/s3/s3cmd).

This change fixes the issue by localizing path separators (as is done elsewhere s3cmd) when creating the local file path.