Updating versions of dependencies

Change-Id: I00cf00f56c26c54421a8325e9bf07085ad6c9750
Updating required packages

Change-Id: I8b0ed3ab55b8ac5035c08f81bcd77bfe0cf74ae4
Update README and Travis config with correct package set.

texlive-latex-extra is needed for the etoolbox package, which is required
by polyglossia.

The GNU FreeFont font which we use is included in the texlive-fonts-extra
package.

Change-Id: I87fac431ad5951f21f92f55a9412eb6f8e27a786