add elements() methods

lib/main.js

@@ -273,6 +273,48 @@ webdriver.prototype.elementByName = function(value, cb) {
   this.element('name', value, cb);
 };
 
+webdriver.prototype.elements = function(using, value, cb) {
+    var _this = this;
+
+    var req = http.request(
+      _this.getOpts({url:'/elements'}), function(res) {
+        res.setEncoding('utf8');
+
+        var data = "";
+        res.on('data', function(chunk) { data += chunk.toString(); });
+        res.on('end', function() {
+          try{
+            var obj = JSON.parse(strip(data));
+          } catch (e) {
+            return cb ('Not JSON response', data)
+          }
+          if (obj.status > 0) {
+            cb(obj, null);
+          } else {
+            cb(null, obj.value);
+          }
+        });
+    });
+
+    req.write(JSON.stringify({
+        using : using,
+        value : value
+    }));
+    req.end();
+};
+
+webdriver.prototype.elementsByLinkText = function(value, cb) {
+  this.elements('link text', value, cb);
+};
+
+webdriver.prototype.elementsById = function(value, cb) {
+  this.elements('id', value, cb);
+};
+
+webdriver.prototype.elementsByName = function(value, cb) {
+  this.elements('name', value, cb);
+};
+
 webdriver.prototype.elementByCss = function(value, cb) {
   this.element('css selector', value, cb);
 };