Fix map fieldtype issue

[minsikzzang]

• Issue fixed in this PR
  Invalid field type (map<string, unsigned int>) #21

module FacebookAds
  module FieldTypes
    class Object < Base
...  
      def deserialize(value, session = nil)
        value.is_a?(String) ? JSON.parse(value) : value
      end		    
...

API response is JSON format data, and it's already decoded in APIResponse class, so value in deserialize method always should be hash format (decoded JSON object / hash). Somehow If it receives string value from API server, still needs to be parsed.

[minsikzzang]

@alanho please let me know if you have any comment / feedback,
Thanks

[minsikzzang]

any feedback or plan for merge @alanho ?

[facebook-github-bot]

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[antonkey]

+1. I applied the patch in my project and waiting for this PR to be merged

[yokuba]

+1. Patch worked for me.

[nicolascochin]

+1 Also worked for me

[Micka33]

+1 also worked for me!