tab complete! yay!

Signed-off-by: Ava Hahn <ava@sunnypup.io>

src/sym.rs

@@ -96,6 +96,10 @@ impl SymTable {
         self.0.iter()
     }
 
+    pub fn keys(&self) -> std::collections::hash_map::Keys<String, Symbol> {
+        self.0.keys()
+    }
+
     pub fn update(&mut self, other: &mut SymTable) {
         /* updates self with all syms in other that match the following cases:
          *   * sym is not in self