sferik/twitter — pull request #435 by korny (2013-07-31 13:33:14+00:00)
Title: Add AlreadyPosted error for "Status is a duplicate"

We have `AlreadyRetweeted` and `AlreadyFavorited`, but Twitter is also failing when you tweet something twice. This PR adds a specific error class to handle these errors.

We want to use it in our code as such:

```ruby
def announce video
Twitter.update message_for_video(video)
rescue Twitter::Error::AlreadyPosted
# ignore
end
```