Add note about protocol organization

[k4y3ff]

Add a note in "Polymorphism"about separating protocols and records into separate files.

/cc @puredanger because this was an imminently useful tangent

[sumbach]

May also be good to mention require-ing the namespace where a record is defined (to ensure it's compiled, even if you don't use any of the Clojure symbols from that namespace directly).

[k4y3ff]

@sumbach Wait, are my issues spamming everyone in the Cognitect org right now? And if so, sorry not sorry?

¯_(ツ)_/¯
;D

[sumbach]

(っ^‿^)っ No problem, @kpfell!

My GH account auto-watched the repo when it was created--I suspect the same for some or all of the Cognitects. I'm enjoying following along.

@cognitect/employees: if you want to unsubscribe, https://github.com/cognitect/clojure-lab/subscription