Added option to put version number in package name dynamically.

[natewalck]

I think this accomplishes what we want without any weird side effects.

The name key looks like it is only use for the output file name, so it seems safe to inject the version number in there if a version variable is present in the original string:

    <key>name</key>
    <string>SuppressSetupAssistant-${version}.pkg</string>
    <key>version</key>
    <string>1.0</string>

Would become:

print(build_info['name'])
SuppressSetupAssistant-1.0.pkg

[gregneagle]

This is much simpler and less problematic than your previous version.

[gregneagle]

Now write some documentation.