also put the new panic mod under version control

src/panic.rs

@@ -0,0 +1,19 @@
+use crate::value::Value;
+use crate::vm::CallFrame;
+
+#[derive(Debug, Clone, PartialEq)]
+pub enum PanicMsg {
+    NoLetMatch,
+    NoFnMatch,
+    NoMatch,
+    Generic(String),
+}
+
+#[derive(Debug, Clone, PartialEq)]
+pub struct Panic {
+    pub msg: PanicMsg,
+    pub frame: CallFrame,
+    pub scrutinee: Option<Value>,
+    pub ip: usize,
+    pub call_stack: Vec<CallFrame>,
+}