v0.7.0

This is a major release with following features.

• kemal-session-file is now deprecated and FileStorage support is built-into kemal-session itself. (Thanks @neovintage )
• Session::StorableObject is not a class anymore and you can use it by including Session::StorableObject (Thanks @neovintage )

class UserStorableObject
  JSON.mapping({
    id: Int32,
    name: String
  })
  include Session::StorableObject

  def initialize(@id : Int32, @name : String); end
end

• Various bug fixes