Fix json serialization and deserialization and JSON 1.5.5 compatability

Update to work with json gems released in the last 8 months. Do not assume that JSON.parse() will directly create a DataBagItem with .raw_data attribute.

This fixes problems chef-solo clients using JSON 1.5.5+ have with reading KnifeSoloDataBag created data bag items.

 rspec tests also updated to reflect new behavior and exercise travis CI environments with another chef version along with JSON 1.5.5 or JSON 1.5.4 type of behavior.