GPUify

[navidcy]

We should make sure that Brusselator runs smoothly and efficiently on a GPU.

[rveltz]

it does not because of N[1, 1] += params.E * grid.nx # note that fft(constant) = constant * nx in calcN!.

What is this line for btw?

[navidcy]

The Brusselator solution has nonzero mean and this the nonlinear component of that.

[glwagner]

I think we just need CUDA.@allowscalar?