Add requirement to demonstrate code understanding

Added a requirement to demonstrate understanding of code implementation.

Author: philipbl

_labs/nibbletorrent-peer.md

@@ -283,6 +283,7 @@ To pass off this lab, you will need to demonstrate to me or the TA that your pee
 1. Contact the tracker (1 point)
 2. Download a file correctly (1 point) from multiple peers *at once* (1 point)
 3. Upload a file to other peers (1 point), including yourself (1 point)
+4. Demonstrate understanding of your code (1 point)
 
 To demonstrate this, follow these steps:
 
@@ -292,6 +293,8 @@ To demonstrate this, follow these steps:
 
 3. Stop your second peer, and then using the command line option, limit the peers you download from to only your first peer and restart your second peer. This will verify that you can download the whole file from your first peer. Verify that the file has been downloaded correctly.
 
+At the end, I will ask you questions about your code, how you implemented it, and why you implemented it in that way. You must demonstrate to me that you **understand** your code and your design decisions.
+
 ## Resources
 
 - [A good description of how torrents work and how to write a peer in Go.](https://blog.jse.li/posts/torrent/)