GMT repository now on GitHub

Added by Paul about 3 years ago

The entire GMT repository has been converted from subversion to git and is now available at The current subversion repository was frozen on August 12, 2018 but is still available as read-only. However, no updates to it will occur and we expect to take it down soon. Users who have used the svn checkout command to obtain the latest GMT code will need to follow new directions on the Building GMT page.