problems with ruby gem ns-api

I am trying to build an app in Rails. For my app I need to use the ns-api (dutch railways) in order to get from them the trains timetables. It exists as a gem (http://ift.tt/2fWp0YV) I use the bundler and I get the message that all the gems are ok, but when I am trying to create a controller it gives me the error that it does not recognise NSclient . This happens also when I use "require 'ns_client'" in my controller or in my configuration file. I think that although the bundler seems to work , the gem is not compatible with my Rails (ver 5.0.0) or my ruby version. Any way that I could solve this ?

Thank you in advance

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