Kotlin codelab

Based on official taking advantage of kotlin codelab

Steps:

• ContactsAdapter
  • visibility modifiers
  • properties
  • constructor
  • val Vs var
  • single line methods
  • [] and +=
• Contact
  • data classes
  • Parcelize annotation
• ContactViewHolder
  • init/join declaration and assignment
  • Contact?
  • lambdas
  • string templates
• ContactDetailDialog
  • companion object
  • @JVMStatic
  • default parameters
  • lateinit
  • ? ?: !!
  • extension methods
  • longToast
  • apply/let
• ContactsActivity
  • when
  • Android extensions to avoid findViewById
• ContactsRepository
  • use
  • delegates