in order to execute the tutorial scripts in General lattice optimization, you need the sgroup tool, which should be downloaded and installed. The code sgroup is a utility which allows to determine the space group and symmetry operations of a crystal structure.
After the download, you will get a tar.gz file, go to the directory where you saved this file and execute the following commands.
$ tar xfvp DownloadedFile.tar.gz
$ cd SpaceGroups
$ cp sgroup $EXCITINGSCRIPTS
Now, you have everything you need for starting and performing the general lattice optimization.
As concerns numpy, it seems to be strange if you cannot find it. Check again your installation of python and of numpy. More information about numpy can be find at http://www.numpy.org/.