Remove underscore as a dependency from the modules package.

packages/modules/package.js

@@ -10,7 +10,6 @@ Npm.depends({
 });
 
 Package.onUse(function(api) {
-  api.use("underscore");
   api.use("modules-runtime");
   api.mainModule("client.js", "client");
   api.mainModule("server.js", "server");

packages/modules/process.js

@@ -24,4 +24,9 @@ if (typeof process.env !== "object") {
   process.env = {};
 }
 
-_.extend(process.env, meteorEnv);
+var hasOwn = Object.prototype.hasOwnProperty;
+for (var key in meteorEnv) {
+  if (hasOwn.call(meteorEnv, key)) {
+    process.env[key] = meteorEnv[key];
+  }
+}