Windows support

These are a few changes to better support Windows.  We may want to add a warning to the documentation that we don't really want to support Windows, but are just including it as is.
According to https://www.npmjs.org/doc/misc/npm-scripts.html (search for ENVIRONMENT), as long as grunt is a dependence in package.json, the local "grunt" will be available, in which case this change does not affect behavior at all - local grunt is still used. Not sure what happens if both local and global grunt are installed, but I would guess the local has precedence.