add normalize(::Accumulator, p)

[tpapp]

Sometimes when I count things, I am more interested in percentages than absolute values. I wonder if you would consider a PR along the lines of

function Base.normalize{T,V}(acc::Accumulator{T,V}, p=1)
    _norm = norm(collect(values(acc)), p)
    Accumulator(Dict(key => value/_norm for (key,value) in acc.map))
end

(obviously with documentation, tests, etc).

[kmsquire]

I think the idea is reasonable, although I think the output should be something other than Accumulator. I don't have any bright ideas about exactly what that should be, though.

[tpapp]

Perhaps a Dict?

[kmsquire]

Sure, that would work.