Is this intended behaviour?

Hello,

Congrats for this gem. It's very useful!
I find that this works as expected:

```
puts Romajify::Converter.hepburn('すし')
# => sushi
```

But sometimes I need to romanise things like:

```
puts Romajify::Converter.hepburn('少し遅れる')
# => 少shi遅reru
```

Any idea @emsk on how to do this?

Thanks,
Claudio