Add MsgPack Marshal and Unmarshal function（Add Test Case And Change return value to unnamed）

[piyongcai]

Note: Marshal max digits is 31. it decimal.IntPart large than 31,it will be lose extra digits.

[piyongcai]

Before diving into the implementation I would like to see a few unit tests. They are handy in case of any refactors, bug catching and implementation changes that could happened in the future

Test Case was added.

[mwoss]

Thanks for providing test cases @piyongcai :) I will try to review your code later this week or next to one, as I need to get familiarized with MsgPack before doing a proper review.