title: pushover + curl --form-string: is badly used
body: <p>I'm trying to use <a href="https://pushover.net/api/client" rel="nofollow noreferrer">pushover</a> and getting the following error:</p>
  
  <pre class="lang-sh prettyprint-override"><code>$ /usr/bin/curl -s \
    --form-string "token=mysecrettoken" \
    --form-string "user=mysecret user" \
    --form-string "hola!" \
    https://api.pushover.net/1/messages.json
  
  curl: option --form-string: is badly used here
  curl: try 'curl --help' or 'curl --manual' for more information
  
  </code></pre>
  
  <p>What am I doing wrong?</p>
  
  <pre><code>curl --version                                       
  curl 7.47.0 (x86_64-pc-linux-gnu)
  </code></pre>