add Box2D 2.3; add sudo apt-get install libsfml-dev libgl1-mesa-dev libglu1-mesa-dev libglew-dev libxi-dev
Reading package lists...
Building dependency tree...
Reading state information...
libgl1-mesa-dev is already the newest version.
libglew-dev is already the newest version.
libglu1-mesa-dev is already the newest version.
libxi-dev is already the newest version.
libsfml-dev is already the newest version.
The following packages were automatically installed and are no longer required:
  libappindicator1 libbox2d0 libindicator7 python-appindicator python-support
Use 'apt-get autoremove' to remove them.
0 upgraded, 0 newly installed, 0 to remove and 26 not upgraded.; remove extlibs/ from .gitignore