[remove] DiffCallback, registration.puml

[remove] ViewContract, Observable, Observer

[add] Refactor RoomMainActivity with rx

[clean] Typo Finish, roomResponseSubject

[add] Refactor RoomInputKeyActivity with rx

[add] Refactor RoomCreateActivity with BaseActivity

[add] Refactor RoomListViewModel with rx

[fix] Dispose CompositeDisposable on Pause

[update] Refactor with BaseActivity and BaseViewModel

[add] Observable of toast and navigation to BaseViewModel

[add] BaseActivity

[add] Error handling

[fix] Refactor create room with rxjava

[fix] Hide subject

[fix] Initialize CopositeDisposable

[clean] indent

[add] Refactor room list with rxjava

[fix] If registed, screen transition

[fix] Do not user base model

[add] Base model

[add] Refactor registration with rxjava

[remove] Log

[add] Registration error handling

[add] Refactor registration with rxjava

[add] RxJava, RxAndroid

[add] Mvvm uml

[add] DiffUtil

[add] Save model

[add] ModelLocaner

[update] Combine observable