Add Stan

[WardBrian]

Stan is a statistical modeling language.

It's syntax looks like this:

data {
  int<lower=0> N;
  array[N] int<lower=0,upper=1> y; // or int<lower=0,upper=1> y[N];
}
parameters {
  real<lower=0,upper=1> theta;
}
model {
  theta ~ beta(1,1);  // uniform prior on interval 0,1
  y ~ bernoulli(theta);
}

From https://github.com/KDE/syntax-highlighting/blob/master/data/syntax/stan.xml