Update packages list + fix sources.list

Update is required because old versions of packages may not be available at the
time of `docker build`.

Recent versions of ubuntu image already contains `universe` category:

$ sudo docker run ubuntu /bin/cat /etc/apt/sources.list
deb http://archive.ubuntu.com/ubuntu precise main universe
deb http://archive.ubuntu.com/ubuntu precise-updates main universe
deb http://archive.ubuntu.com/ubuntu precise-security main universe
$