Now IA don't fire a cake if the kart is driving too slow. Also correct some comments.
Add a new Gold Driver achievement.
Fix a build issue for Travis CI.
Revert "Now IA don't fire a cake if the kart is driving too slow. Also correct some comments."

This reverts commit 9030291340cff5f1786267034cb2040d2088aa8e.
Clean up some minor coding style issues
Fixed potential crash if RelationInfo should not exist, which I saw
once while a decline was in progress), started some minor refactoring.
Merge branch 'master' of https://github.com/gupascal/stk-code into gupascal-master
Fixed some merging issues.
Conflicts:
	data/achievements.xml
	src/achievements/achievement_info.hpp
Merge branch 'master' of github.com:supertuxkart/stk-code