added new Mode called CareerMode in which each Contender gets to fight every other Contender

(Contender.java)
added in 3 public int variables:
totalWon - to keep track of won battles
totalDrawn - to keep track of Mutual Annihiliation
totalLost - to keep track of lost battles
added in setHealth() method to be able to heal Contenders before a battle

(LastManStanding.java)
updated to reflect the Mode structure of the other Modes

(RandomMatchUp.java)
moved code into matchUp() and battle() methods

(CareerMode.java)
added a new file that uses a lot of the battle() method code from the RandomMatchUp mode

(YogiBear.java, JayGundam.java and NathanRobo.java)
commented out their a.name + " attacks!" println() from their AI() methods

Out of interest, below are the results of the CareerMode with the current Contenders - the number signifies total wins:
All Contenders have participated
Adam's : 3W 4D 7L 
Boo Boo : 8W 0D 6L 
Omega : 0W 7D 7L 
Freedom : 13W 1D 0L 
Blitz : 10W 2D 2L 
Max : 4W 1D 9L 
Tania : 8W 1D 5L 
Yogi Bear : 1W 2D 11L  
Merge pull request #14 from marekgorski-user/master

CareerMode added to project - allows each Contender to battle with every other Contender