Introduced the saveObject() method for JointModelSample objects in order to serialise them to disk (#431).
Added support for truncated prior distributions e.g. you can now apply a normal prior to a strictly positive parameter and jmpost will take care of adjusting the density accordingly (#429).
Included new Gamma distribution survival model (#411).
Reworked LOO calculations to apply to each individual submodel and disabled LOO calculations for the overall joint model (#402).
