Fix imports for SPM

Author: pvzig

SlackKit/Sources/Client+EventHandling.swift

@@ -21,6 +21,8 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 // THE SOFTWARE.
 
+import Foundation
+
 internal extension Client {
 
     //MARK: - Pong

SlackKit/Sources/Client.swift

@@ -21,6 +21,7 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 // THE SOFTWARE.
 
+import Foundation
 import Starscream
 
 public final class Client: WebSocketDelegate {

SlackKit/Sources/ClientOptions.swift

@@ -21,6 +21,8 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 // THE SOFTWARE.
 
+import Foundation
+
 public struct ClientOptions {
 
     let simpleLatest: Bool?

SlackKit/Sources/History.swift

@@ -21,7 +21,10 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 // THE SOFTWARE.
 
+import Foundation
+
 public struct History {
+    
     internal(set) public var latest: NSDate?
     internal(set) public var messages = [Message]()
     public let hasMore: Bool?

SlackKit/Sources/IncomingWebhook.swift

@@ -21,6 +21,8 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 // THE SOFTWARE.
 
+import Foundation
+
 public struct IncomingWebhook {
 
     public let url: String?

SlackKit/Sources/OAuthServer.swift

@@ -21,6 +21,7 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 // THE SOFTWARE.
 
+import Foundation
 import Swifter
 
 internal protocol OAuthDelegate {

SlackKit/Sources/Server.swift

@@ -21,6 +21,7 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 // THE SOFTWARE.
 
+import Foundation
 import Swifter
 
 internal enum Reply {

SlackKit/Sources/SlackKit.swift

@@ -21,6 +21,8 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 // THE SOFTWARE.
 
+import Foundation
+
 public final class SlackKit: OAuthDelegate {
 
     internal(set) public var oauth: OAuthServer?