Added docs for $resolved and changelog for upcoming 2.1.0 release (#874)

* Added docs for $resolved and changelog for upcoming 2.1.0 release

* Improved documentation for $resolved

Author: Jacob Wenger

changelog.txt

@@ -0,0 +1 @@
+feature - Added `$resolved` property to `$firebaseArray` and `$firebaseObject` to get synchronous access to the loaded state.

docs/reference.md

@@ -11,6 +11,7 @@
   * [`$bindTo(scope, varName)`](#bindtoscope-varname)
   * [`$watch(callback, context)`](#watchcallback-context)
   * [`$destroy()`](#destroy)
+  * [`$resolved`](#resolved)
 * [`$firebaseArray`](#firebasearray)
   * [`$add(newData)`](#addnewdata)
   * [`$remove(recordOrIndex)`](#removerecordorindex)
@@ -22,6 +23,7 @@
   * [`$ref()`](#ref-1)
   * [`$watch(cb[, context])`](#watchcb-context)
   * [`$destroy()`](#destroy-1)
+  * [`$resolved`](#resolved-1)
 * [`$firebaseAuth`](#firebaseauth)
   * Authentication
     * [`$signInWithCustomToken(authToken)`](#signinwithcustomtokenauthtoken)
@@ -174,8 +176,8 @@ obj.$save().then(function(ref) {
 
 ### $loaded()
 
-Returns a promise which is resolved when the initial object data has been downloaded from the database.
-The promise resolves to the `$firebaseObject` itself.
+Returns a promise which is resolved asynchronously when the initial object data has been downloaded
+from the database. The promise resolves to the `$firebaseObject` itself.
 
 ```js
 var obj = $firebaseObject(ref);
@@ -288,6 +290,32 @@ unwatch();
 Calling this method cancels event listeners and frees memory used by this object (deletes the
 local data). Changes are no longer synchronized to or from the database.
 
+### $resolved
+
+Attribute which represents the loaded state for this object. Its value will be `true` if the initial
+object data has been downloaded from the database; otherwise, its value will be `false`. This
+attribute is complementary to the `$loaded()` method. If the `$loaded()` promise is completed
+(either with success or rejection), then `$resolved` will be `true`. `$resolved` will be
+`false` before that.
+
+Knowing if the object has been resolved is useful to conditionally show certain parts of your view:
+
+```js
+$scope.obj = $firebaseObject(ref);
+```
+
+```html
+<!-- Loading state -->
+<div ng-if="!obj.$resolved">
+  ...
+</div>
+
+<!-- Loaded state -->
+<div ng-if="obj.$resolved">
+  ...
+</div>
+```
+
 
 ## $firebaseArray
 
@@ -461,8 +489,8 @@ list.$indexFor("zulu"); // -1
 
 ### $loaded()
 
-Returns a promise which is resolved when the initial array data has been downloaded from the
-database. The promise resolves to the `$firebaseArray`.
+Returns a promise which is resolved asynchronously when the initial array data has been downloaded
+from the database. The promise resolves to the `$firebaseArray`.
 
 ```js
 var list = $firebaseArray(ref);
@@ -547,6 +575,32 @@ function compare(a, b) {
 Stop listening for events and free memory used by this array (empties the local copy).
 Changes are no longer synchronized to or from the database.
 
+### $resolved
+
+Attribute which represents the loaded state for this array. Its value will be `true` if the initial
+array data has been downloaded from the database; otherwise, its value will be `false`. This
+attribute is complementary to the `$loaded()` method. If the `$loaded()` promise is completed
+(either with success or rejection), then `$resolved` will be `true`. `$resolved` will be
+`false` before that.
+
+Knowing if the array has been resolved is useful to conditionally show certain parts of your view:
+
+```js
+$scope.list = $firebaseArray(ref);
+```
+
+```html
+<!-- Loading state -->
+<div ng-if="!list.$resolved">
+  ...
+</div>
+
+<!-- Loaded state -->
+<div ng-if="list.$resolved">
+  ...
+</div>
+```
+
 
 ## $firebaseAuth