GASP is not properly introduced

In <http://www.openbookproject.net/thinkCSpy/ch04.html#gasp> and <http://www.openbookproject.net/thinkCSpy/ch08.html> the GASP project is not introduced at all in the text. It is assumed that python-gasp is installed on all user systems, and if not that the user has the knowledge to install it.

At the very least we should link to the LP page <http://launchpad.net/gasp-code> or better yet the download/install page at <http://dev.laptop.org/pub/gasp/downloads/>.

The lack of a proper introduction has caused a bit of user confusion (see <http://www.theartfulscientist.com/2008/03/16/how-to-install-pyobjc-pygame-and-gasp-on-mac-os-x-for-python-tutorial/> and <http://stackoverflow.com/questions/1024862/>