Change-log for quick update 0.5.1

-Rearranged the switches and instruction pictograph at the hub a little bit
-Added B-2 gun and an initial upgrade to the hub to teach these mechanics a bit faster
-Some changes to level 1-1, trying to bring up the action and difficulty at the start of the game
-Secondary attack button no longer does melee attack when you have no secondary weapon. Input is ignored instead.
-Fixed bug where you could take damage after finishing a level
-Fixed bug where level summary screen would display 'new record' at values of zero
-Fixed bug where there could be multiple instances of the music playing