init: first working impl of determinant

types: added initial matrix definition and impl blocks

src/main.rs

@@ -0,0 +1,9 @@
+use types::matrix::Matrix;
+
+mod types;
+fn main() {
+    println!("Hello, world!");
+    let m = Matrix::from_str("1,2\n3,4".to_string());
+    let d = m.determinant();
+    println!("{}", d);
+}