Shield and Magic arrow

Hi,
Small update V0.3

• Modified the waves to make it more balanced (maybe too easy now ;p)
• Hero now fires automatically, no more left click frenzy héhé
• New skill: 
  • Shields:
    •  Creates 3 shields rotating around the player, can take 10 hits each before disappearing. Returns after 10 seconds
    • Cost: 500
    • dmg: 10
    • Cd when reached 10hit: 10seconds
  • Magic Arrow
    •  Sends a magic arrow that target a creep automatically.
    • dmg: 50

• UI: Shop item now display a title
• Bugfix: 
  • Xp UI is now updated when a skill is unlocked.
  • Unlock button on FireRate and Move improvement stays visible when bought.