First version used in another paper ("Anti-aliasing of geophysics for probabilistic inversions of 3-D geological forward models", submitted to Geoscientific Model Development). Currently implements a range of simple Metropolis-Hastings algorithms including Metropolis random walk; adaptive Metropolis random walk (Haario et al. 2001); preconditioned Crank-Nicholson random walk (Cotter et al. 2013); a vanilla Hamiltonian Monte Carlo sampler; and parallel tempering.