0.2.4 - quick-switch weapons, reload with r, sparks more free, first art

Features added

• You can quick-switch to your slammer weapon by right-clicking (by popular demand!)
• Pressing R lets you reload
• Sparks now spawn from projectiles if the projectile hits an enemy
• Shoot pitch is slightly randomized
• Enemy destroy pitch is less slow
• First artwork is added!!
• Camera does a zoom-in effect if you hit space!  (placeholder trigger, real game won't be based on button press)