Update convergence sampling signature to use `state`

[mileslucas]

AbstractMCMC.jl/src/sample.jl

Line 209 in d961513

while !isdone(rng, model, sampler, samples, i; progress=progress, kwargs...)

I think this should be updated to be

isdone(rng, model, sampler, samples, state, i; progress=progress, kwargs...)

to coincide with the immutable samplers (#42, #56), which would be breaking (unfortunately).

Thoughts on this? I'm happy to PR, just let me know if this has downstream effects that I'll need to address, too.

[devmotion]

I would be fine with adding it, it seems reasonable (even though I don't think that the linked PRs imply that one has to do it). As long as we follow semver and make a breaking release we should not worry about downstream packages here I think (additionally, I believe it's not used in many downstream packages).