Changing sdl2 dependency to libsdl2

Author: Databean

.travis.yml

@@ -2,5 +2,5 @@ language: cpp
 before_install: 
  - sudo add-apt-repository ppa:antumdeluge/sdl2 -y
  - sudo apt-get update -y
- - sudo apt-get install sdl2 -y
+ - sudo apt-get install libsdl2 -y
 script: make tests