`Distributions.Multinomial`

seems to accept a vector of probabilities that doesn’t sum to one, even if in the code reported in the documentation it should have `ckeck_args`

true by default. Why is that ?

```
using Distributions #0.21.6
julia> p_v = [0.1,0.4,0.3,0.8]
4-element Array{Float64,1}:
0.1
0.4
0.3
0.8
julia> a = Multinomial(10000, p_v)
Multinomial{Float64,Array{Float64,1}}(n=10000, p=[0.1, 0.4, 0.3, 0.8])
julia> b = rand(a)
4-element Array{Int64,1}:
1010
3980
2977
2033
julia> c = sum(b,dims=2) ./ 10000
4-element Array{Float64,1}:
0.101
0.398
0.2977
0.2033
julia> sum(c)
1.0
julia> isprobvec([0.1,0.4,0.3,0.8])
false
```