make code that throw exception return exit code 1

CHANGELOG.md

@@ -9,6 +9,7 @@
 * remove `nil` parser constant [#332](https://github.com/jcubic/lips/issues/332)
 * replace `undefined` with `#void`, and `null` with `#null`
 * characters are again unboxed into strings by JavaScript code [#329](https://github.com/jcubic/lips/issues/329)
+* code that throw exception now return exit code 1
 ### Features
 * add `vector-for-each` and `vector-copy!` function from R7RS
 * add `string-for-each`, `string-downcase`, and `string-upcase` from R7RS

bin/lips.js

@@ -101,6 +101,7 @@ function print_error(e, stack) {
     if (stack) {
         console.error(e.stack);
         console.error(strace);
+        process.exit(1);
     } else {
         console.error(e.message);
         console.error('Call (stack-trace) to see the stack');