Update README.md
Update README.md
Bugfixes and features

Features
+Extended collision detection so that it now has effect
+Added proper bullet physics and hit detection
+Added UI Text for score and lives
+Added start of death screen
+Added asteroid death
+Added bullet death
+Added reset player to center after death
+Added gun cooldown for bullet firing

Bugfixes:
+Fixed undefined error.
+Code cleanup and removal of debug logging.
Address merge conflict.
Quick change log tonight

Features
+Added level transitions (with bugs)
+Added loop/play once for sounds (badly)
+Misc additions for gameplay

Bugfixes
+No logged bugfixes fixed.
Merge remote-tracking branch 'origin/master' into gh-pages