fix readme

fixs the readme

config/error_codes.go

@@ -32,6 +32,12 @@ var NO_DATA_FOUND = &common.DawnError{
 
 // 500s
 
+var DATABSE_CONNECTION_ERROR = &common.DawnError{
+	Name:        "DATABSE_CONNECTION_ERROR",
+	Description: "Cannot connect to database",
+	Code:        500,
+}
+
 var INTERNAL_SERVER_STANDARD_ERROR = &common.DawnError{
 	Name:        "INTERNAL_SERVER_ERROR",
 	Description: "Unkown internal server error occurred",