[Ethereum] Where is the code for web3 version 0.20.x

I'm using the following:

truffle(development)> version
Truffle v4.0.5 (core: 4.0.5)
Solidity v0.4.18 (solc-js)
truffle(development)> web3.version
{ api: '0.20.3',
  node: [Getter],
  getNode: { [Function: get] request: [Function: bound ] },
  network: [Getter],
  getNetwork: { [Function: get] request: [Function: bound ] },
  ethereum: [Getter],
  getEthereum: { [Function: get] request: [Function: bound ] },
  whisper: [Getter],
  getWhisper: { [Function: get] request: [Function: bound ] } }

Apparently my truffle console is using v0.20.3 of web3.js. However, the web3.js releases shows that it skips from 0.19 to 1.0-beta.