adding support for lambda/callables to the new update function

Author: Jonathan Garcia Lima

jsonpath_rw/jsonpath.py

@@ -432,7 +432,10 @@ def find(self, datum):
 
     def update(self, data, val):
         for field in self.reified_fields(DatumInContext.wrap(data)):
-            data[field] = val
+            if hasattr(val, '__call__'):
+                data[field] = val.__call__(data[field])
+            else:
+                data[field] = val
         return data
 
     def __str__(self):
@@ -466,7 +469,10 @@ def find(self, datum):
             return []
 
     def update(self, data, val):
-        data[self.index] = val
+        if hasattr(val, '__call__'):
+            data[self.index] = val.__call__(data[self.index])
+        else:
+            data[self.index] = val
         return data
 
     def __eq__(self, other):