ES5
If your browser does not support ECMAScript 6, you will need to run babel to compile an ES5-compatible version of the ES6 mpw-js code.
- Install npm.  On OS X, you can use 
brew install npm. - Install babel.  With npm installed, you can use 
npm -g install babel-cli babel-preset-es2015 - Build the ES5-translation of the ES6 code.  From this directory, just run 
make.