Make model hashes deterministic

Strings included in the hash are randomly salted, breaking
caching between different runs. See
https://docs.python.org/3/reference/datamodel.html#object.__hash__

pyphi/models/actual_causation.py

@@ -177,7 +177,7 @@ def __eq__(self, other):
         return self.ria == other.ria
 
     def __hash__(self):
-        return hash(('CausalLink', self._ria))
+        return hash(self._ria)
 
     def __bool__(self):
         """An |CausalLink| is ``True`` if |alpha > 0|."""

pyphi/models/cuts.py

@@ -122,7 +122,7 @@ def __eq__(self, other):
         return self.indices == other.indices
 
     def __hash__(self):
-        return hash(('NullCut', self.indices))
+        return hash(self.indices)
 
 
 class Cut(namedtuple('Cut', ['from_nodes', 'to_nodes']), _CutBase):

pyphi/models/mechanism.py

@@ -235,7 +235,7 @@ def __eq__(self, other):
         return self.ria == other.ria
 
     def __hash__(self):
-        return hash(('MICE', self._ria))
+        return hash(self._ria)
 
     def to_json(self):
         return {'ria': self.ria}