Add approval callback function for Boxcars::ActiveRecord for changes to the data

[francis]

• add approval callback function
• clean up keyword key setting and related tests

[AKovtunov]

I think that right now is the perfect time to make your own wrapper method for eval code which will check for dangerous code inside.

like

def evaluate_input(code)
   ... strip `code` from dangerous methods ...
  eval code
end

and use it all around, since you already started using it in many places and probably will be more

[francis]

good point.