Alias Vector2, Array, etc when no numpy

[fwkoch]

Current implementation ignores math properties when numpy isn't available as a dependency. It would be nice to add basic aliases for these property types (eg. Vector2 is List of floats with min_length = max_length = 2).

The biggest difficulty here is that these aliased property types will not have all the numpy/vectormath methods. That means code that requires these methods will fail. I think maybe this isn't too big a problem - packages can require properties[math] if they need the methods. Possibly a warning on import if numpy isn't available?

[fwkoch]

This has an open pull request (#189) but I'm not convinced of the value so I'm hesitant to merge...