Travis CI: revert, giving up update for now.

.travis.yml

 language: cpp
-sudo: false
 
 os:
   - linux
@@ -8,17 +7,9 @@ compiler:
   - gcc
   - clang
 
-addons:
-  apt:
-    packages:
-    - libglfw-dev
-    - libglfw3-dev
-    - libxrandr-dev
-    - libxrandr-dev:i386
-    - libxi-dev
-    - libxi-dev:i386
-    - libxxf86vm-dev
-    - libxxf86vm-dev:i386
+before_install:
+  - if [ $TRAVIS_OS_NAME == linux ]; then sudo add-apt-repository -y ppa:pyglfw/pyglfw && sudo apt-get update -qq && sudo apt-get install -y --no-install-recommends libglfw3-dev libxrandr-dev libxi-dev libxxf86vm-dev; fi
+  - if [ $TRAVIS_OS_NAME == osx ]; then brew update && brew install glfw3; fi
 
 script: 
   - make -C examples/opengl_example