Change NSCoding to Codable Protocol

[ulayuno]

I think it would be interesting to change the actual NSCoding protocol to the Codable protocol that Apple presented in the last WWDC. By doing so we can keep this awesome app up to date.

[zahid119]

This can be helpful: http://www.json4swift.com/

[meghs91]

I found handy tool for generating template based mode class online http://www.jsoncafe.com/ this might be helpful