Improved API and examples

• Add conversion for NamedTuple <-> (nim) Tuple, Dict <-> Table
• Improve the API ergonomics
• Add examples
• Add memory graph
• Improve readme

First alpha release

This is an alpha release with basic functionnality handling numerical types, string, bool and tuples / arrays of said types.

It can be useful to defer Matrix multiplication to Julia. Be aware of the Row major vs Column major issue and Julia compile-time / JIT delay.