[update] Toast and navigation with observer pattern

[add] Navigation observable and Toast observable to BaseViewModel

[add] Navigation observer and Toast observer to BaseActivity

[add] NavigationMessage, ToastMessage

[add] Mvvm uml

[add] DiffUtil

[add] Save model

[add] ModelLocaner

[update] Combine observable

[add] Enter room with key

[add] Start RoomInputKeyActivity

[update] Room update interval

[add] RoomCreateActivity to back button

[fix] Add observer at onResume, Remove observer at onPause

[update] Unable develop mode

[add] Refresh room state

[fix] Schedulers

[add] Save member id

[add] Start RoomMainActivity

[add] Create room

[add] Start RoomCreateActivity

[clean] Remove log

[add] Save room id

[add] Enter room

[add] Update java version

[clean] Remove long

[add] Refresh room list

[update] Javadoc

[add] Use observer pattern

[add] Start RoomListActivity