Merge pull request #428 from ruijunhuang2010/master

update
Merge pull request #429 from ruijunhuang2010/master

redirect registered open challenges to registration page
Merge pull request #430 from ruijunhuang2010/master

update
Merge pull request #431 from ruijunhuang2010/master

resume from accepted challenges
Merge pull request #432 from ruijunhuang2010/master

resume challenge game from profile page
Merge pull request #27 from ChrisBoesch/master

update
debug #9
Merge pull request #433 from LI-HE/master

debug #9
debug #10
Merge pull request #435 from LI-HE/master

debug #10
Merge pull request #21 from ChrisBoesch/master

update