Implemented another observer pattern in RegattaFragment and
RegattaActivity.
Added option item in RegattaActivity. Added new strings for refresh
option.
Extracted methods from the huge callServerAndGenerateCheckinData
method. Each server request is inside an individual method. Introduced
anonymous class URLData. URLData is used to share data between Network
requests instead of lots of final string objects. Improved readability
of CheckinManager class.
Extracted CheckinMangaer logic from HomeFragment. Introduced new
Interface inside CheckinManager. Introduced new abstract activity
CheckinDataActivity. Classes that inherit from CheckinDataActivity
implement a notification method. See GoF Observer Pattern.