Can't sample multidimensional arrays

[amrods]

I am opening a new issue here. I first mentioned it in issue 161 but didn't get attention. I think this is a very easy fix.

sample has trouble dispatching method 8 of the methods table:

sample(a::AbstractArray, dims::Tuple{Vararg{Int64,N}} where N; replace, ordered)

so sample(1:100, (2,2)) gives a methods error:

julia> sample(1:100, (2,2))
ERROR: MethodError: no method matching sample!(::MersenneTwister, ::UnitRange{Int64}, ::Array{Int64,2}, ::MersenneTwister; replace=true, ordered=false)

I think this is because the rng argument is repeated in line 393 of sampling.jl

[nalimilan]

Thanks. Can you suggest a fix or make a pull request?