How to reload an updated library?

[Tory S. Anderson]

In this case, I'm talking about the Helm package. I follow it on git and 
sometimes will `git pull` to update it, then can make it. But the only way I 
know to implement the new changes in emacs is to restart emacs. I tried 
evaluate-buffer on one of the main library files, but it didn't seem to do the 
trick. Restarting emacs is a pain if I have many ongoing projects; how can I 
implement the updates to the package without restarting emacs?