Define open_timeout and read_timeout independently

Hi, is there any reason why we can't define open_timeout and read_timeout independently?

I would be happy to implement it; I think the following code would be enough:

```ruby
 def open_timeout=(new_timeout)
 @http.open_timeout = new_timeout
 end

 def read_timeout=(new_timeout)
 @http.read_timeout = new_timeout
 end
```

