title: Node JS request-promises POST method doesn't recognize a string
body: <p>In order to connect my node.js module with another server I use 'request-promise' library. When I want to post something which looks like this:</p>
  
  <pre><code>rp.({
     method: 'POST',
     headers:{
      'Content-Type': 'text/plain',
      'Authorization': ''
  },
     uri: 'https://myendpoint.com',
     body:{
       name: 'here is my a name',
       code: 'here is my code',
       location: 'here is my location'
     }
  }).then(...)
  </code></pre>
  
  <p>But always when I try to use this function I get error message like this:</p>
  
  <pre><code>  RequestError: Error: Argument, error, options.body.
    TypeError: First argument must be a string or Buffer
  </code></pre>
  
  <p>All of my arguments in body are strings. Also I tried the same method on postman and that worked for me. So what I do wrong? </p>