Add basic versino of cp-nest implementation

added 1 commit

5575accb - fix assignment of prior bounds

added 1 commit

c23aa7a7 - add warning if seed isn't specified

@gregory.ashton I'm going to list a few things that I think we should look into before merging. We may not get them all working, but I think we should consider them before adding a version in.

There's an issue with the Gaussian prior, the current implementation can't sample from a prior with an infinite extent.
We should add a placeholder for how custom jump proposals can be added.
It would be nice to be able to resume from a previous run. I'm not sure if this is something cpnest supports. EDIT: This has a placeholder.