--url-base-path option passed to fdoc convert is ignored from convertes 

This seems due to the fact that on service.rb, the method used by view is done this way:

```
def base_path
  base_path = @schema['basePath']
  if base_path && !base_path.end_with?('/')
    base_path + '/'
  else
    base_path
  end
end
```

and `@schema['basePath']` does not get overridden by option passed to fdoc convert Cli command.
