feat: Replace bad matrices with interpolated ones
feat: Replace bad matrices with interpolated ones

Add automatic replacement of badly specified transition matrices
with ones obtained by interpolating the two nearest well-defined
matrices.

This feature addresses an issue raised with commit ae8d537 and
related to the wrong specification of certain transition matrices
in the Markov chain caused by various errors, particularly:

 - maximum tolerance for the solution (1e-2) reached;
 - iteration limit (1e4) reached.

In both cases, the matrix is still returned even if bad.

Provided that the last matrix in the generated Markov chain is
correct, the function now automatically replaces all wrong ones
with the corresponding interpolated versions.

Resolves: #1

federicomariamassari/willow-tree