Add PromiseKit dependency

- Added PromiseKit dependency

Carthage/Checkouts/PromiseKit/Extensions/MapKit/Sources/MKDirections+Promise.swift

@@ -0,0 +1,38 @@
+import MapKit
+#if !PMKCocoaPods
+import PromiseKit
+#endif
+
+/**
+ To import the `MKDirections` category:
+
+    use_frameworks!
+    pod "PromiseKit/MapKit"
+
+ And then in your sources:
+
+    import PromiseKit
+*/
+extension MKDirections {
+#if swift(>=4.2)
+    /// Begins calculating the requested route information asynchronously.
+    public func calculate() -> Promise<Response> {
+        return Promise { calculate(completionHandler: $0.resolve) }
+    }
+
+    /// Begins calculating the requested travel-time information asynchronously.
+    public func calculateETA() -> Promise<ETAResponse> {
+        return Promise { calculateETA(completionHandler: $0.resolve) }
+    }
+#else
+    /// Begins calculating the requested route information asynchronously.
+    public func calculate() -> Promise<MKDirectionsResponse> {
+        return Promise { calculate(completionHandler: $0.resolve) }
+    }
+
+    /// Begins calculating the requested travel-time information asynchronously.
+    public func calculateETA() -> Promise<MKETAResponse> {
+        return Promise { calculateETA(completionHandler: $0.resolve) }
+    }
+#endif
+}