refactor imports (#69)

Author: ferrine

pymc_experimental/tests/test_bart.py

@@ -3,7 +3,7 @@
 import pytest
 from numpy.random import RandomState
 from numpy.testing import assert_almost_equal, assert_array_equal
-from pymc.tests.test_distributions_moments import assert_moment_is_expected
+from pymc.tests.distributions.util import assert_moment_is_expected
 
 import pymc_experimental as pmx