title: Where to find d3 api document of old version(2.9.6)?
body: <p>I'm using some library which is built based on d3.js. But the d3 version the lib is using is 2.9.6. there's are some api differences between 2.9 and 3.0. like attr method of selection is not support in 2.9 but available in 3.0. So I'm sure how can I know how is the api like for version 2.9. I have been searching around. I can't find specific api reference for 2.9, current d3 api reference is for the latest d3 version. </p>
  
  <p>Does someone knows where to find the api documentation for d3 old version?</p>