json content detection is broken

[Yohann Rebattu]

function is_json_response check if content type is equal to "application/json", in my request the json content type is "application/json; charset=utf-8".
would it be better to check if content-type.startwith('application/json') instead of content-type=='application/json'

edit: this is fixed by #23

[Brandon Wood]

This is currently being addressed in #23