Support hessian 2.0 decode. #8

* Add Date hessian 2.0 decode.
* add double, int hessian 2.0 support
* decode compact long, but four octet longs not impl
* support decode hessian string 2.0
* add java HashMap decode
* Read hessian 2.0 Object and Class
* support hessian 2.0 ref
* support hessian 2.0 readType
* support read hessian 2.0 List
* update byte to 0.2.1, use getInt8()
* update hessian 2.0 readme
Support hessian 2.0 encoder.

* int encode hessian 2.0
* encode hessian 2.0 long
* Support encode hessian 2.0: double, date, bytes and string
add hessian 2.0 decoder
change decoder switch and if else to hash map code detect
add readRefId() to share code logic between v1.0 and v2.0
encode hessian 2.0 map
encode hessian 2.0 list
Merge pull request #9 from fengmk2/hessian-v2

Hessian v2.0 decode and encode support, fixed #8