Add PromiseKit dependency

- Added PromiseKit dependency

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

@@ -0,0 +1,38 @@
+# STALLED
+
+This project is no longer maintained because its promises and API are not up to standard. You can use it, but we will not maintain it unless the API is improved (feel free to PR!).
+
+# PromiseKit EventKit Extensions ![Build Status]
+
+This project adds promises to Apple’s EventKit framework.
+
+## CocoaPods
+
+```ruby
+pod "PromiseKit/EventKit" ~> 6.0
+```
+
+The extensions are built into `PromiseKit.framework` thus nothing else is needed.
+
+## Carthage
+
+```ruby
+github "PromiseKit/EventKit" ~> 3.0
+```
+
+The extensions are built into their own framework:
+
+```swift
+// swift
+import PromiseKit
+import PMKEventKit
+```
+
+```objc
+// objc
+@import PromiseKit;
+@import PMKEventKit;
+```
+
+
+[Build Status]: https://travis-ci.org/PromiseKit/EventKit.svg?branch=master