[website] PHP warnings

[vieks]

http://p5js.org/tutorials/trigonometry/

[limzykenneth]

Seems to be several links broken, I'll try to fix this but I'm not sure how complete this tutorial really is but I can at least fix the PHP errors.

[lmccart]

yes this is an in progress tutorial (it's not listed on the tutorials page yet), but if you'd like to fix I think the php links just need an extra "../". otherwise I'll be back at this in a few days and can fix it then. thanks!