Refactor KL divergence distance for Simulator

[ricardoV94]

This was actually never refactored for the new Simulator / V4:

pymc/pymc/distributions/simulator.py

Lines 276 to 293 in c76b9b9

	class KullbackLiebler:
	"""Approximate Kullback-Liebler."""
	def __init__(self, obs_data):
	if obs_data.ndim == 1:
	obs_data = obs_data[:, None]
	n, d = obs_data.shape
	rho_d, _ = cKDTree(obs_data).query(obs_data, 2)
	self.rho_d = rho_d[:, 1]
	self.d_n = d / n
	self.log_r = np.log(n / (n - 1))
	self.obs_data = obs_data
	def __call__(self, epsilon, obs_data, sim_data):
	if sim_data.ndim == 1:
	sim_data = sim_data[:, None]
	nu_d, _ = cKDTree(sim_data).query(self.obs_data, 1)
	return self.d_n * np.sum(-np.log(nu_d / self.rho_d) / epsilon) + self.log_r