Add unit test to confirm negative integer literals work without quotation marks

Fixes #244

Author: TedDriggs

core/src/from_meta.rs

@@ -842,6 +842,12 @@ mod tests {
         assert_eq!(fm::<u32>(quote!(ignore = 5000i32)), 5000u32);
     }
 
+    #[test]
+    fn negative_int_without_quotes() {
+        assert_eq!(fm::<i8>(quote!(ignore = -2)), -2i8);
+        assert_eq!(fm::<i32>(quote!(ignore = -255)), -255i32);
+    }
+
     #[test]
     #[allow(clippy::float_cmp)] // we want exact equality
     fn float_without_quotes() {