update processing.js

I was working on a project involving noise, and I tried to use noiseSeed, but I couldn't get different patterns for different inputs to noise seed. Then I found this: https://github.com/processing-js/processing-js/issues/131 so I'm guessing the issue is already fixed and just needs to be brought into khan academy.

@kevinbarabash I remember Kevin mentioned in this thread https://github.com/Khan/live-editor/issues/470 that "our fork of processing.js has changes that would either need to be pushed upstream or ported to the newer version". Just thought that might jump start the discussion about the update.

Start by comparing Khan Academy’s fork of processing.js with the newer upstream version, then read processing-js issue 131 and Khan/live-editor issue 470 for the known differences. Done means the relevant processing.js update is incorporated into the live editor and noiseSeed produces different patterns for different inputs.

Written by the indexing model from the issue text.