Arabic characters in node-wit are not recognised by wit.ai

Arabic characters are not recognised by wit.ai when sent through client.message().
I get either an empty entities or the wrong one:
```
  {"_text":"سلام","entities":{},"msg_id":"18pE0IifO6KKNPw0y"}
```
**Example of Arabic message:**
```
client.message('سلام', {})
.then((data) => {
  console.log(JSON.stringify(data));
})
.catch(console.error);
```
This issue does not apply to English.