function for computing tension probability

[lukashergt]

@williamjameshandley, do you have the code to compute things like suspiciousness and its corresponding tension probability? Could we add that somewhere? Maybe as a function taking multiple Samples instances in samples.py?

Have you tried computing this from MCMC data?

[AdamOrmondroyd]

I've put some things together in my suspiciousness package, might be some use here