fix #131: parameter data driven with pair keys

tests/data/demo_parameters.yml

@@ -2,6 +2,9 @@
     name: "user management testset."
     parameters:
         - user_agent: ["iOS/10.1", "iOS/10.2", "iOS/10.3"]
+        - username-password:
+            - ["test1","111111"]
+            - ["test2","222222"]
     variables:
         - device_sn: ${gen_random_string(15)}
         - os_platform: 'ios'
@@ -28,7 +31,7 @@
 #     name: create user
 #     parameters:
 #         - user_id: [1001, 1002, 1003]
-#         - username-password: ${parameterize(account.csv)}
+#         - username-password: ${P(account.csv)}
 #     api: create_user($user_id, $username, $password, $token)
 #     validate:
 #         - {"check": "status_code", "expect": 201}