v1.3

This release does not bring new observables or major new features, but instead a couple of small improvements and fixes, the most important ones being:

• Several hadronic parameters from lattice QCD have been updated to the new FLAG 2019 average
• flavio.statistics.probability.combine_distributions now supports multivariate PDFs
• The CKM elements used by the wilson package for Wilson coefficient basis translation are now set to the values set in flavio (thanks to @jackypheno for reporting a related bug, #78)
• Likelihoods in the flavio.statistics.likelihood module now cache their observable predictions for repeated calls (thanks @peterstangl!)