Innately handle nested model disposal

[ondreian]

I have found that as my Chaplin applications grow it makes sense to nest models, some working examples might be a Post with a child collection of images that are used in subviews.

However, upon saving/changing to a different instance of the parent model a quasi-Singleton/ghost model bug can emerge on the nested models, so that a complete new Post may be initialized but somehow the images are referencing another post's images.

Initially I solved this by manually disposing my nested models via a super in Model::dispose method of every model, but recently I patched my version of Chaplin.Model::dipose to contain the following:

attr.dispose?() for attr of @attributes

I am not sure if there is a reason that the Model::dispose method doesn't already contain this fallback for nested models, but I have not noticed any unintended results from it, and it has made my model declaration a bit more straightforward.

[ondreian]

@paulmillr sorry, was just going through and closing issues that seemingly were stagnant in my feed.