add online users information services.
add equals and hashCode method for UserDTO.
display the number of currently online registered user in footer.
use ng-bind span to display onlineUsersCount
Merge pull request #106 from iv404/online-users

Online users information.
[UPDATE] Do not rejudge accepted status
[UPDATE] Refactor count() to rejudgeStatusCount()
Merge pull request #122 from mzry1992/do-not-rejudge-accepted-status

[UPDATE] Do not rejudge accepted status
add equals and hashCode methods for every DTO about article.
add equals and hashCode method for CodeDTO.
add equals and hashCode methods for every DTO about contest.
add equals and hashCode methods for every DTO about contest problem.
add equals and hashCode methods for ContestUserDTO.
add equals and hashCode methods for DepartmentDTO.
add equals and hashCode methods for LanguageDTO.
add equals and hashCode methods for every DTO about message.
add equals and hashCode methods for every DTO about problem.
add equals and hashCode methods for every DTO about status.
add equals and hashCode methods for every DTO about team.
add equals and hashCode methods for every DTO about team user.