Sanitizing Plist UTF8 strings #2482

I like to resolve this issue asap. I would appreciate your feedback on the solution.
I'm willing to do whatever it takes to fix this. Let me know if this is the way to do it.

Thank you, Ladi
Yes please :) Something like the following:

```ruby
if RUBY_VERSION >= '1.9'
  text.encode('UTF-8', 'binary', :invalid => :replace, :undef => :replace, :replace => '')
else
  text
end
```

And also update the docs to reflect this behaviour.