add button style for sign up screen
Merge branch 'master' of https://github.com/dst-hackathon/socialradar-android

# By PhubaseTiewthanom (3) and others
# Via mekeerati (2) and others
* 'master' of https://github.com/dst-hackathon/socialradar-android:
  handle exception
  Introduce RestProvider.
  Commit missing files.
  Change the referenced menu of Login page; changing from main.xml to login.xml.
  Rename Answer model to Option.