Merge pull request #58 from sli-fox/steph_branch

Minor tweaks
fixed crash after final wave would end (game tried to access nullptr for next wave stats)
merging to remote
Merge pull request #59 from sli-fox/jeremy

Jeremy
Fixed critters activation bug
Merge pull request #60 from sli-fox/marky_branch

Fixed critters activation bug
Reverted a fix, added critters_remaining attribute to CritterWave
Merge pull request #61 from sli-fox/marky_branch

Reverted a fix, added critters_remaining attribute to CritterWave
Critter activation bug fix