Merge pull request #40 from wright-group/getitem

Allow getitem to get subcurve keys if key is not in self

attune/curve/_base.py

@@ -125,7 +125,9 @@ def __add__(self, other):
         return self_
 
     def __getitem__(self, key):
-        return self.dependents[key]
+        if key in self.dependents:
+            return self.dependents[key]
+        return self.subcurve[key]
 
     def __setitem__(self, key, value):
         value = copy_.deepcopy(value)