broadcast behavior of Corpus

[baggepinnen]

I would argue that the following is unintuitive, and would like for broadcasted functions over a corpus to return an array with the result of the function applied to each document in the corpus. If this is deemed a good idea, I would be willing to submit a PR if desired.

julia> length(crps)
12

julia> length(crps[1])
160427

[aviks]

👍