Test using dream from BayesianTools

[josephguillaume]

There is another implementation of dream already on CRAN.
https://cran.r-project.org/web/packages/BayesianTools/index.html

Let's test whether it can be used as a replacement for ours.

[WillemVervoort]

Slightly unrelated, but this was part of our discussion: What does CRAN say about packages not on CRAN:

Packages on which a CRAN package depends should be available from a mainstream repository: if any mentioned in ‘Suggests’ or ‘Enhances’ fields are not from such a repository, where to obtain them at a repository should be specified in an ‘Additional_repositories’ field of the DESCRIPTION file (as a comma-separated list of repository URLs) or for other means of access, described in the ‘Description’ field.
A package listed in ‘Suggests’ or ‘Enhances’ should be used conditionally in examples or tests if it cannot straightforwardly be installed on the major R platforms. (‘Writing R Extensions’ recommends that they are always used conditionally.)

Orphaned CRAN packages should not be strict requirements (in the ‘Depends’, ‘Imports’ or ‘LinkingTo’ fields, including indirectly). They are allowed in ‘Suggests’ if used conditionally, although this is discouraged.

So I think we can include packages from a different repos and not on CRAN as long as they are in "Suggests" or "Enhances"