More flexible isapprox

[andyferris]

I got:

MethodError: isapprox has no method matching isapprox(::Array{Float64,1},::FixedSizeArrays.Point{2,Float64})

Perhaps we could define isapprox(a,b; kwargs...) with mixtures of FixedArrays and AbstractArrays?

[andyferris]

PS - this is another issue that I believe wouldn't exist if FixedSizeArrays inherited from AbstractArray...