Topic: auto_link not working

So, I have read (and experienced) that auto_link is no longer working. I have two questions: 1) why was auto_link removed; and 2) how do I actually use something like rinku https://github.com/tanoku/rinku? The reason I ask the first question is, if auto_link was removed for a purpose (which I assume it was), it is probably a bad idea to start using a plugin that offers the same functionality. The reason I ask the second question is that I do not understand how to use the gem (eg-whenever I try to use it, I get