Use p5.js or p5.min.js in index.html

[shiffman]

I noticed that the minified versions of the library are referenced in index.html. I think we should probably use the full versions for things like the friendly error messages, etc. (This can eventually be preference with an editable template, etc.)

[catarak]

In retrospect this is obvious... but I did not realize the friendly errors aren't in the minified versions. Finally switching this out.

[catarak]

also I don't know how to test whether or not this is working... help? @shiffman

[lmccart]

I removed the friendly errors from the most recent version of p5.js because they need another pass to make them consistent and work well. So I think it makes sense for us to go with p5.min.js for the time being.