Don't use "objects" in lib/compiler/index.js

The "objects" module will be removed.

See #442.

lib/compiler/index.js

@@ -1,6 +1,20 @@
 "use strict";
 
-let objects = require("../utils/objects");
+function processOptions(options, defaults) {
+  let processedOptions = {};
+
+  Object.keys(options).forEach(name => {
+    processedOptions[name] = options[name];
+  });
+
+  Object.keys(defaults).forEach(name => {
+    if (!processedOptions.hasOwnProperty(name)) {
+      processedOptions[name] = defaults[name];
+    }
+  });
+
+  return processedOptions;
+}
 
 let compiler = {
   /*
@@ -42,8 +56,7 @@ let compiler = {
   compile: function(ast, passes, options) {
     options = options !== undefined ? options : {};
 
-    options = objects.clone(options);
-    objects.defaults(options, {
+    options = processOptions(options, {
       allowedStartRules: [ast.rules[0].name],
       cache:             false,
       dependencies:      {},