Overrode canvas.stroke

[alexturpin]

On level 17, I was getting weird errors when using canvas.stroke, errors saying it wasn't a function. I console logged its value and saw that it was '#F00'. I did that by accident on the previous level when figuring out canvas.strokeStyle. Maybe that ought to be protected against somehow?

[alexturpin]

There is still a pretty easy way to do the level, combined with a bit of trial and error: https://gist.github.com/anonymous/59b90b98f7655c795ee8

[pppery]

Changes to canvas.stroke no longer persist across levels as of #442. I see no reason to prevent you from doing this in one level - you're shooting yourself in the foot and JavaScript is saying "Ouch!".