Add by_date and by_payee getters

Author: Felixoid

zenmoney/zenobject.py

@@ -51,6 +51,9 @@ def by_account(self, value):
             if o.incomeAccount == value or o.outcomeAccount == value:
                 yield o
 
+    def by_date(self, value):
+        return self._by_attr('date', value)
+
     def by_id(self, value):
         return self._by_attr_uniq('id', value)
 
@@ -60,6 +63,9 @@ def by_incomeAccount(self, value):
     def by_outcomeAccount(self, value):
         return self._by_attr('outcomeAccount', value)
 
+    def by_payee(self, value):
+        return self._by_attr('payee', value)
+
     def by_shortTitle(self, value):
         return self._by_attr_uniq('shortTitle', value)