Contact and Group cache was created

Contact and Group cache was  created
SortedListOf class was used for groups and contacts store

SortedListOf class was used for groups and contacts store. New package
com.example.utils was created for this class.
Groups tests were modified to hamcrest notation

Groups tests were modified to hamcrest notation. Assertions changed to
junit assertions with hamcrest notation.
Contacts tests were modified to use hamcrest notation

Contacts tests were modified to use hamcrest notation. Assertions were
changed to assertions from junit package.