[Pharo-project] pharo-project.org: small updates website

Hi, -> The download button now goes to http://www.pharo-project.org/pharo-download, not the zip (because there are now 3) -> updated http://www.pharo-project.org/pharo-download for the platform specific zip files -> added a page for GSOC: http://www.pharo-project.org/community/google-soc Marcus