Turing.jl: Guide on http://turing.ml/latest/guide.html is broken

[trappmartin]

Currently, the example code on http://turing.ml/latest/guide.html is incorrect. See issue #562 for the correct code.

@cpfiffer could you have a look at this, please?

[cpfiffer]

Absolutely, probably should have caught this when the last changes to MCMCChain came through.

[cpfiffer]

Updated. I'll go through the rest of the documentation to make sure the MCMCChain stuff is current.

[trappmartin]

Thanks a lot!