Minor improvments

Hi,
here are some minor improvements:
* start tournament with all currently available implementations of players (tested on fresh system)
* fix bundle-command to start visual_spectator
* in player.rb, define instance methods as such to avoid NoMethodError - allows to dynamically add/remove players during tournament; method "relative_points" can be called without instance, causing NoMethodError when defined as class method
* background-position-x is not CSS3 standard, only working in Webkit (Chrome, Safari), but neither Gecko (Firefox) nor Presto (Opera); leads to 5 identical button-images. replaced with background-position