Gulp polish update

Hey there. This is just a post game jam update addressing some issues found in the previous version. 

Fixes:

• turned the bass notes for music down
• adjusted the time is takes for enemies to spawn
• adjusted some bigger enemies hitpoints
• adjusted the color of some sprites to not confuse with enemy projectiles 

New:

• a new background
• pickups now past your max weapon upgrade will reward health when max pick up is reached
• added pickup counter to ui