Fix flaky model replication test

[meissnereric]

The test that fails sometimes is:

testing/core/factor_graph_test.py::FactorGraphTests::test_replicate_simple_model

It only fails on Linux builds and only occasionally. First step would be to reproduce the failure then debug why it's happening.

[meissnereric]

============================= test session starts ==============================
platform darwin -- Python 3.4.4, pytest-3.5.1, py-1.6.0, pluggy-0.6.0 -- /Users/travis/.pyenv/versions/3.4.4/bin/python3.4
cachedir: .pytest_cache
rootdir: /Users/travis/build/amzn/MXFusion, inifile: setup.cfg
plugins: cov-2.5.1
collected 100 items

_________________ FactorGraphTests.test_replicate_simple_model _________________
self = <factor_graph_test.FactorGraphTests testMethod=test_replicate_simple_model>
    def test_replicate_simple_model(self):
        m = mf.models.Model(verbose=False)
        m.x = mfc.Variable()
        d = mf.components.distributions.Normal(mean=mx.nd.array([0]), variance=mx.nd.array([1e6]))
        m.x.set_prior(d)
        m2, var_map = m.clone()
        # compare m and m2 components and such for exactness.
        self.assertTrue(all([k.uuid == v.uuid for k, v in var_map.items()]))
        self.assertTrue(all([k.uuid == v.uuid for k, v in
>                       zip(m.components.values(), m2.components.values())]))
E       AssertionError: False is not true
testing/core/factor_graph_test.py:147: AssertionError

[meissnereric]

Setting environment variables from .travis.yml
$ export PYTHON=3.4.4