sampling and log-pdf for Gaussians now works
method will stay for now
removed TODO lines since I added tests a while ago
added a bunch of tests for the new Gaussian distribution class
added log-sum-exp and log-mean-exp trick and a unit test for each
added new method to evaluate the log-likelihood of multiple f functions and a unit test
first version of unbiased estimator for log-marginal-likelihood
few documentation updates