Fix package/publish problems on Windows

There are two problems with packaging/publishing tasks on Windows:

* Without the windowsVerbatimArguments flag, spawn strips off the quotes
from the arguments, causing bad command lines for the git commands in
npmPublish.
* The publish task needs to strip off the drive letter from the full
path, or else jake will interpret it as a namespace and fail to find the
file task.
Merge pull request #244 from panopticoncentral/master

Fix package/publish problems on Windows