Factor.Util.Resolution.exec no longer handles executable scripts.

This commit prefixes the file path in script_parser with a shell (sh). The reason this is now required is that Factor now searches for a binary before executing the command in Factor.Util.Resolution.exec and if the binary doesn't exist, nil is returned.  By prefixing the filename with 'sh' and not running the file itself as an executable, Resolution.exec perfoms as expected.