define an API for the parser generator with basic failing test cases

tests/c_parser_generator.rs

@@ -0,0 +1,19 @@
+
+use lambda_mountain::parser_generator::compile;
+
+#[test]
+fn cfg1() {
+   let grammar = compile("entry-point := /a/");
+   assert_eq!(
+      grammar.run("").to_string(),
+      "Error in String at line 1 column 1: expected /a/ in rule entry-point"
+   );
+   assert_eq!(
+      grammar.run("a").to_string(),
+      "Success"
+   );
+   assert_eq!(
+      grammar.run("aa").to_string(),
+      "Error in String at line 1 column 1: expected EOF in rule entry-point"
+   );
+}