Update kanren dependency

Author: brandonwillard

requirements.txt

@@ -7,7 +7,7 @@ tensorflow-estimator-2.0-preview>=1.14.0.dev2019090801
 pymc3>=3.6
 multipledispatch>=0.6.0
 logical-unification>=0.2.2
-kanren @ git+https://github.com/pymc-devs/kanren.git@symbolic-pymc#egg=kanren-0.2.3
+miniKanren>=0.2.5
 cons>=0.1.3
 toolz>=0.9.0
 sympy>=1.3