Build failure for new consumers.

[jazzz]

Problem

Using logos-chat in an application requires the liblogosdelivery dynamic library to be available. It is auto generated, when the library is build, but requires nix to be installed. If nix is not installed, then the process silently fails.

This creates an obscure series of linker errors

Criteria

• Consumers have clear directions on how to use logos-chat in their projects.
• Directions do not assume that any particular build system is installed
• cargo build works on Linux and MacOs, for consumers who have followed the directions/

Optional

• Consumers do not require 'nix' to use logos-chat