Make new example for Unsupported Distribution

[wd60622]

After #123, the unsupported_distribution example doesn't make sense and was removed.
There should be a new example to show this off.

The pareto distribution might be a good candidate for this

import numpy as np

from conjugate.distributions import Gamma, Pareto
from conjugate.models import pareto_gamma

prior = Gamma(1, 1)
data = [1, 2, 1, 2, 3]

posterior = pareto_gamma(n=len(data), ln_x_total=np.log(data).sum(), prior=prior, x_m=1)


posterior_samples = posterior.dist.rvs(size=1000)
posterior_predictive_samples = Pareto(x_m=1, alpha=posterior_samples).rvs(size=1000)