fix XCode 10.2, Swift 5 errors (#322)

Author: krezzoid

.swift-version

@@ -1 +1 @@
-4.0
+5.0

Source/Logging.swift

@@ -74,23 +74,23 @@ public class RxBluetoothKitLog: ReactiveCompatible {
     }
 
     static func v(_ message: @autoclosure () -> String) {
-        log(with: .verbose, message: message)
+        log(with: .verbose, message: message())
     }
 
     static func d(_ message: @autoclosure () -> String) {
-        log(with: .debug, message: message)
+        log(with: .debug, message: message())
     }
 
     static func i(_ message: @autoclosure () -> String) {
-        log(with: .info, message: message)
+        log(with: .info, message: message())
     }
 
     static func w(_ message: @autoclosure () -> String) {
-        log(with: .warning, message: message)
+        log(with: .warning, message: message())
     }
 
     static func e(_ message: @autoclosure () -> String) {
-        log(with: .error, message: message)
+        log(with: .error, message: message())
     }
 }