Allow mixins to be separated.

[flamendless]

Hi, I think that mixins are also useful for acting as a sub-class that can be shared between multiple classes instead of making another base class. With that level of abstraction, i think that implemented mixins should have their own container.
Here's a snippet:

local Human = classic:extend()
local Power = classic:extend()
function Power:magic() end

Human:implement(Power)

function Human:cast()
  --instead of 
  Human:magic()
  --i suggest:
  Human.Power:magic()
end

Also, Power class should have it's own self table.
To access the Human class from Power: self.parent.human_name

[gingerbeardman]

what are the benefits of this proposition?