New Versions of Ruby do not include ostruct by default

[cloke]

This pull request includes a minor change to the lib/interfax/object.rb file. The change imports the ostruct library to ensure the OpenStruct class is available for use.

• lib/interfax/object.rb: Added require "ostruct" to import the ostruct library.

[mohanklein]

ah I just wanted to create a PR with the exact same fix but then I saw you already did the exact same thing :-) thanks!