Styled my buttons

Added: i new file with the style for my buttons (DrumButton.xml)
Fixed: added the styled to my buttons in the drumMachine layout
Drum machine background

Added: just added a background to the drum machine layout
Drum Machine Background

Fix: just fixed the background, so it actually works
Changed the gravity of the layout

Added: the gravity is now changed to centered at the bottom for the
buttons
Title for the Drum machine

Add: just added a drum machine title to the drum mechine layout
Just fixed the buttons in the drum machine

Fix: 7 put of the 8 buttons were not working but they are now fixed