add StateTotalRecord for Iowa

pyaccuwage/fields.py

@@ -207,6 +207,10 @@ class BlankField(TextField):
     def parse(self, s):
         pass
 
+class ZeroField(BlankField):
+    def get_data(self):
+        return '0' * self.max_length
+
 class CRLFField(TextField):
     def __init__(self, name=None, required=False):
         super(TextField, self).__init__(name=name, max_length=2, required=required, uppercase=False)