We use Bones as our code loader in this case though depending on your use case a straight node `require()` might be simple enough. The npm JS api is quite usab

We use Bones as our code loader in this case though depending on your use case a straight node `require()` might be simple enough. The npm JS api is quite usable, so it was simply a matter of establishing a directory for plugins (in this case `~/.tilemill/node_modules`) and using the npm API to install, uninstall, etc. plugin packages to there. We identify plugin packages by the `tilemill` tag in the npm repo and each plugin is required to declare their compatibility with a particular tilemill version at the `engines` key.