`hilbert(S::Space{<:PeriodicLine},f,z)` calls domain`(f::AbstractVector)`

[mjp98]

On line 14 of periodicline.jl there appears to be a typo, leading to a call to domain(f::AbstractVector) which is not defined.

function hilbert(S::Space{<:PeriodicLine},f::AbstractVector,z::Number)
    S2=setdomain(S,Circle())
    hilbert(S2,f,mappoint(domain(f),Circle(),z))-hilbert(S2,f,-1)
end

I think the last line should read hilbert(S2,f,mappoint(domain(S),Circle(),z))-hilbert(S2,f,-1)?

A similar issue occurs on line 24. I would be happy to put together a pull request to fix this.

[dlfivefifty]

Great, thanks!