Consider creating custom "mmcc" class

[njtierney]

I'm creating the n_chain helper function at the moment, and it would be useful to know whether the object is something that was created with mcmc_to_dt so it can be dispatched via S3 methods.

Current method is:

n_chain.data.table <- function(x){
    max(x$chain)
}

New method, if the class structure gets implemented, would be:

n_chain.mmcc <- function(x){
  max(x$chain)
}

[samclifford]

I'm on board.