added bullet directory to .gitignore
added bullet directory to .gitignore

philippotto/GP2013,MaxReimann/Troen,MaxReimann/troen-simulator,philippotto/GP2013,MaxReimann/Troen,MaxReimann/Troen,MaxReimann/Troen,MaxReimann/troen-simulator,philippotto/GP2013,philippotto/GP2013,philippotto/GP2013,MaxReimann/troen-simulator