Transition on next level
Set player invulnerable for 300ms when collision

Enemies won’t damage the player on every game update
Fix Player#setInvulnerable

setTimeout sets this = window
However, the third and following arguments to setTimeout will be sent to
the callback function as arguments, this means we can send in this as an
argument called player and thereby access this.
Fixed css
Merge pull request #60 from CrazyDave1/transition-on-next-level

Transition on next level
Merge pull request #62 from scmx/player-immune-after-damaged

Player immune after damaged
Give player a healthbar
Refactor HealthBar to accept color option

Give Player a green healthbar (might be bad)
Default to red healthbar
Add Hitpoint to #levelPanel view