Implement Monad class.

[mepcotterell]

https://en.wikipedia.org/wiki/Monad_(functional_programming)

• [ ] Document Monad class.
• [ ] Write tests for Monad class.
• [ ] Implement Monad class.

Minimum required functionality:

• 1. M(x).bind(f).value == f(x).value
• 2. M(x).bind(M).value == M(x).value
• 3. M(x).bind(f).bind(g).value == M(x).bind(x => f(x).bind(g)).value

[mepcotterell]

const gaius = require('gaius');
const M = gaius.Monad;

const nums = M([0, 1, 2, 3]).map(n => n+1).bind(Array.from);

const id = x => x;
const num = M(41).map(n => n+1).bind(id);