v0.5.1

• Add method for Wilks' theorem p-value
• Implement weighted matrices in LikelihoodMachine
• Implement non-uniform toy index prior for MCMC
• Add best_possible_log_likelihood method
• Add value/entries/sumw2 setting methods to response matrix objects
• Remove unnecessary storage of response values in matrix builder
• Change behaviour of nuisance bins in matrix builder to use maximum
• Add single-file storage of ResponseMatrix and output of array builder
• Add fold and pseudo_chi2 methods to LikelihoodMachine