Fix frameRate() example

[toolness]

This fixes the frameRate() example mentioned in processing/p5.js-website#196. I think.

If this is the "proper" fix, I'm not actually sure it's all that intuitive--I mean, I could easily see myself calling color() at my top-level code, and a thrown error like TypeError: a._renderer is undefined wouldn't really help me debug it--I wonder if there's a way the friendly error system could throw a less cryptic message?

[lmccart]

this is the correct fix, no p5 functions work outside of setup/draw... if you can think of any good way to catch this error it'd be wonderful, but I haven't come up with anything yet. the main issue is that calling p5 functions before setup fails because p5 hasn't been instantiated yet (this non-automatic global binding of p5 functions is in place to support instance mode, where p5 is wrapped up in one object so as not to pollute the global namespace. so we have to wait to be sure we are working in global mode before adding all the p5 functions). so i'm not how we could catch errors when p5 isn't running? but any thoughts welcome!

[toolness]

Ah, got it... That is a tough problem.

It's a bit hacky, but what if we added an onerror event handler that caught errors during page load and offered help if possible?

Here's an example: http://jsbin.com/riyaco/2/edit?html,console,output

Again, it's hacky, and I'm not sure how many false positives it'd trigger...