Revert "Modify CalabashHelper.run to update absolute paths on Windows to use / instead of \ (fixes #28)"

This reverts commit 8a0bef74a3e3f90d527801463d4981b6b3b1f432.
Expand CalabashHelper to support parameter values which are instances of String, File, URI, or URL (previously only String was supported)
Make sure to escape parameter values since they are pass as XML attributes
Consistent treatment of paths as URIs for transformations

* Since base paths passed to the XSLT transforms are already URIs, no need to add file:/// at the beginning
Make sure the System Id for sources created in ApiRefMojo.createSource is a URI
Merge pull request #30 from sharwell/PathsAreUris

Paths are URIs