Add mmap support to to BSON.jl

using Pkg
pkg"add BSONMmap"

using BSON, BSONMmap
dict = Dict("a" => ones(Float32, 10), Dict("b" => zeros(10)))
BSON.bson("test.bson", dict)

bsload("test.bson", mmaparrays = true) == dict

withenv("BSON_MMAP" => true) do
    BSON.load("test.bson")
end