Log Message:
Update ruby-msgpack to 0.6.2.

2015-07-22 version 0.6.2:

* Fix release workflow: Ruby 2.1 and 2.2 are supported for Windows (2.0 is
  omitted)
* Fix to encode symbols along its encoding
* Fix segmentation fault in minor case

2015-07-01 version 0.6.1:

* Added :compatibility_mode option to Packer#initialize. Default is false. If it
  is set to true, str8 format and bin format family will not be used.