Find by bug

[doliveirakn]

Message I received

However we found that it causes some problems with .where or .find_by methods. Using your example from the ReadMe for the gem it'd look like:

Picture.where(imageable: Product.find(10))

this generates sql like:
SELECT * from pictures WHERE imageable_type = 0 AND imageable_id = 10;

Do you know why this happened? We expect to have a sql like:
SELECT * from pictures WHERE imageable_type = 2 AND imageable_id = 10;

so basically the imageable_type is wrong. Do you know how to fix this?

This PR adds a spec around the issue, a new monkey patch that fixes it, as well as cleans up some general things to make development easier and show that we are supporting Rails 5