Abstract engine burn-in

[connorourke]

• Add default burnin to tinygp engine

  mind_the_gaps/mind_the_gaps/engines/tinygp_engine.py

  Line 69 in ec04e22

  burnin: int,

• Edit main MCMC convergence check loop so that it prints a message before the first run where it burns in

  mind_the_gaps/mind_the_gaps/engines/tinygp_engine.py

  Lines 166 to 171 in ec04e22

  	for iteration in range(num_iterations):
  	if state is not None:
  	mcmc.post_warmup_state = state
  	self.rng_key = mcmc.post_warmup_state.rng_key
  	mcmc.run(self.rng_key, self._lightcurve.times)