Broadcasting weirdness

[Chad Scherrer]

Hi, thanks for this great package!

I'm seeing some strange behavior with broadcasting. It's easy enough to work around, but still seems worth noting:

julia> (zeros(3) .± 1) .± 2
3-element Array{Measurement{Measurement{Float64}},1}:
 0.0 ± 1.0 ± 2.0 ± 0.0
 0.0 ± 1.0 ± 2.0 ± 0.0
 0.0 ± 1.0 ± 2.0 ± 0.0