fix encrypt engine choice bug

Author: rzcoder

package.json

@@ -1,6 +1,6 @@
 {
   "name": "node-rsa",
-  "version": "0.2.20",
+  "version": "0.2.21",
   "description": "Node.js RSA library",
   "main": "src/NodeRSA.js",
   "scripts": {

src/encryptEngines/encryptEngines.js

@@ -2,10 +2,8 @@ var crypt = require('crypto');
 
 module.exports = {
     getEngine: function (keyPair, options) {
-        var engine;
-        if (options.environment === 'browser') {
-            engine = require('./js.js');
-        } else {
+        var engine = require('./js.js');
+        if (options.environment === 'node') {
             if (typeof crypt.publicEncrypt === 'function' && typeof crypt.privateDecrypt === 'function') {
                 if (typeof crypt.privateEncrypt === 'function' && typeof crypt.publicDecrypt === 'function') {
                     engine = require('./io.js');