Add PromiseKit dependency

- Added PromiseKit dependency

Carthage/Checkouts/PromiseKit/Extensions/Bolts/README.markdown

@@ -0,0 +1,47 @@
+# PromiseKit Bolts Extensions ![Build Status]
+
+This project adds promises to Facebook’s [Bolts] framework.
+
+Bolts underlies the entire Facbook SDK.
+
+## Usage
+
+```swift
+someBoltsTask().then { anyObject in
+    //…
+}
+```
+
+## CocoaPods
+
+```ruby
+pod "PromiseKit/Bolts" ~> 6.0
+```
+
+The extensions are built into `PromiseKit.framework` thus nothing else is needed.
+
+## Carthage
+
+```ruby
+github "PromiseKit/Bolts" ~> 3.0
+```
+
+The extensions are built into their own framework:
+
+```swift
+// swift
+import PromiseKit
+import PMKBolts
+```
+
+```objc
+// objc
+@import PromiseKit;
+@import PMKBolts;
+```
+
+
+[Bolts]: https://github.com/BoltsFramework
+
+
+[Build Status]: https://travis-ci.org/PromiseKit/Bolts.svg?branch=master