Add jump feature

 * Stickman can now jump on swipe up gesture.
 * Improved collision checking with missiles to work
   with the jump.
   Removed use of 'missiles_for_collision_check', instead
   loops through whole 'missiles' array.
 * 'y' coordinate for stickman now denotes bottom level
   instead of top level.
   Code can now handle images of different heights, each
   image is scaled in reference of 'standing_bitmap'
Increased toughness of game-play

 * Increased no. of missiles increment rate.
 * Increased both Missile GRAVITY and Stickman GRAVITY
Change splash screen

 * Added new logo (now head and "warzone" text
   is included in same image)
 * Replaced text in buttons with images
 * Changed xml layout
Add animated splash screen logo
Merge branch 'jump_feature'
Updated readme