Revert "Update CGAL and CMake for Linux in Travis-CI"
Revert "Update CGAL and CMake for Linux in Travis-CI"

This reverts commit 53efcf7f10f758635c2e65af0d2669e4ffe8243b.
acgetchell/CDT-plusplus,acgetchell/CDT-plusplus,acgetchell/CDT-plusplus