Add Class Form for challenge_player
Create box for challenge_player
Add an url pattern for challenge_player
 Add challenge_player function, it launches a challenge to player_to_challenge
Remove Class form for challenge_player
Add template tag player_input
Change challenge_player function for player_input template tag
Change order of results for autocompletion with nickname
Change challenge game description
Restore order
Merge pull request #369 from ionel-popescu93/master

Challenge a specific player from Challenges page
[api] Add all group members api.
[api] Bump docs version.
[workshop] Unneeded string in cpanel.