Avoid encoding values as string, for integer grid filters

grid filter for Catapult Transaction "Status" was not working right b/c that is
an integer in the db, but we were passing encoded string value to SA / query

tailbone/grids/filters.py

@@ -591,6 +591,11 @@ class AlchemyIntegerFilter(AlchemyNumericFilter):
                 return True
         return False
 
+    def encode_value(self, value):
+        # ensure we pass integer value to sqlalchemy, so it does not try to
+        # encode it as a string etc.
+        return int(value)
+
 
 class AlchemyBooleanFilter(AlchemyGridFilter):
     """