feat: add getProperty method

package.json

@@ -1,6 +1,6 @@
 {
   "name": "macaca-wd",
-  "version": "1.0.5",
+  "version": "1.0.6",
   "description": "macaca wd client",
   "keywords": [
     "macaca",

wd/lib/commands.js

@@ -1372,6 +1372,26 @@ commands.getAttribute = function() {
   });
 };
 
+/**
+ * getProperty(element, propertyName, cb) -> cb(err, value)
+ *
+ * @jsonWire GET /session/:sessionId/element/:id/property/:name
+ * @docOrder 1
+ */
+commands.getProperty = function() {
+  var fargs = utils.varargs(arguments);
+  var cb = fargs.callback,
+      element = fargs.all[0],
+      propertyName = fargs.all[1];
+  if(!element) { throw new Error('Missing element.'); }
+  if(!propertyName) { throw new Error('Missing property name.'); }
+  this._jsonWireCall({
+    method: 'GET'
+    , relPath: '/element/' + element + '/property/' + propertyName
+    , cb: callbackWithData(cb, this)
+  });
+};
+
 /**
  * isDisplayed(element, cb) -> cb(err, displayed)
  *

wd/lib/element-commands.js

@@ -8,7 +8,7 @@ var _ = require("./lodash")
     elementCallback = callbacks.elementCallback,
     elementsCallback = callbacks.elementsCallback,
     commands = require('./commands');
-  
+
 var elementCommands = {};
 
 /**
@@ -178,6 +178,16 @@ elementCommands.getAttribute = function(name, cb) {
   commands.getAttribute.apply(this.browser, [this, name, cb]);
 };
 
+/**
+ * element.getProperty(propertyName, cb) -> cb(err, value)
+ *
+ * @jsonWire GET /session/:sessionId/element/:id/property/:name
+ * @docOrder 2
+ */
+elementCommands.getProperty = function(name, cb) {
+  commands.getProperty.apply(this.browser, [this, name, cb]);
+};
+
 /**
  * element.getTagName(cb) -> cb(err, name)
  *
@@ -408,7 +418,7 @@ elementCommands.performMultiAction = function (actions, cb) {
  * element.rotate(opts, cb) -> cb(err)
  * opts is like the following:
  * {x: 114, y: 198, duration: 5, radius: 3, rotation: 220, touchCount: 2}
- * 
+ *
  * @jsonWire POST /session/:sessionId/appium/device/rotate
  */
 elementCommands.rotate = function(opts, cb) {