Compose modifies the global RNG

[cstjean]

In Julia 0.4, in a Jupyter notebook, these two scripts yield different results.

srand(23)
display(compose(context()))
rand(1:1000)

srand(23)
rand(1:1000)

Most likely because of this line generating a random ID. Is there any reason for the ID to be random? Can we use a counter, or a private RNG that does not modify the global RNG?

[tlnagy]

I could reproduce with the latest version, #311 introduces a private RNG so we don't modify global state.