Merge pull request #13 from LIHPC-Computational-Geometry/fix-unsound

Remove numbering feature and add unchecked constructors.

Exceptionally this is a non-linear merge as that branch was old and I did not want to modify original commits by rebasing them.

Author: cedricchevalier19

examples/graph.rs

@@ -21,7 +21,7 @@ fn main() -> Result<(), metis::Error> {
         9, 13,
     ];
     let mut part = vec![0x00; 15];
-    Graph::new(1, 2, xadj, adjncy).part_recursive(&mut part)?;
+    Graph::new(1, 2, xadj, adjncy)?.part_recursive(&mut part)?;
     println!("{:?}", part);
 
     Ok(())