fixed find tetgen triangle

Former-commit-id: af1c57eba10563492323b512b83222ae8ce91a05

tutorial/cmake/FindTETGEN.cmake

@@ -8,6 +8,7 @@
 FIND_PATH(TETGEN_INCLUDE_DIR tetgen.h
    ${PROJECT_SOURCE_DIR}/../libigl/external/tetgen/
    ${PROJECT_SOURCE_DIR}/../../external/tetgen/
+   ${PROJECT_SOURCE_DIR}/../external/tetgen/
    /usr/include
    /usr/local/include
    NO_DEFAULT_PATH

tutorial/cmake/FindTRIANGLE.cmake

@@ -14,6 +14,7 @@ FIND_PATH(TRIANGLE_INCLUDE_DIR triangle.h
    /usr/local/include
    ${PROJECT_SOURCE_DIR}/../libigl/external/triangle/
    ${PROJECT_SOURCE_DIR}/../../external/triangle/
+   ${PROJECT_SOURCE_DIR}/../external/triangle/
    NO_DEFAULT_PATH
 )