Rogue Runner v0.3 - Basic Attacks

I've added the traditional basic rogue-like attack - bump into something and do some damage to it.
So, for this we had to implement the 'bumping' action, collision with the enemy, flashing to denote damage, updating the health of the enemy and displaying it's health bar when the enemy has less than maximum health.
I also added a death effect for when it dies. It's not very good. I wish I knew an artist.
There was a bug for a while where the distance clocked up when you killed an enemy. I considered makig it part of the gameplay but decided against it.
The enemy has no AI at the moment - I just wanted to get the attack interaction in first.

Next: ... probably some collecting of items.