charlotte-ruby/impressionist — pull request #157 by yfxie (2014-06-03 03:56:37+00:00)
Title: change impressionable_id type to string

I think it should use string type.
In case, I define to_param on model
and /posts/this-is-my-permalink will result in 0 value saved in column.
It work well in any case if use string type.