Support and use broadcast with mapreduce.

[maleadt]

No description provided.

[maleadt]

julia> mapreduce(+,+,jl(ones(1)), jl(ones(2,2)))
8.0

julia> mapreduce(+,+,ones(1), ones(2,2))
2.0

Looks like we can't implement the implicit map(+, ..., ...) here using Broadcast?

julia> map(+, ones(1), ones(2,2))
1-element Array{Float64,1}:
 2.0

julia> ones(1) .+ ones(2,2)
2×2 Array{Float64,2}:
 2.0  2.0
 2.0  2.0