* Update docs for old releases section in README
Hopefully not many folks are still in the process of transitioning to version 3.
* tweak for future-friendliness
### Documentation for previous releases
-Documentation for v2.3.2 has been made available for the time being at <https://getbootstrap.com/2.3.2/> while folks transition to Bootstrap 3.
+- For v2.3.2: <https://getbootstrap.com/2.3.2/>
+- For v3.3.x: <https://getbootstrap.com/docs/3.3/>
[Previous releases](https://github.com/twbs/bootstrap/releases) and their documentation are also available for download.