Switched convertible extensions over to using one-line property implementations.

# Conflicts:
#	Source/Alamofire.swift

Source/Alamofire.swift

@@ -50,9 +50,9 @@ extension String: URLStringConvertible {
 extension NSURL: URLStringConvertible {
     public var URLString: String {
         #if swift(>=2.3)
-        return absoluteString!
+            return absoluteString!
         #else
-        return absoluteString
+            return absoluteString
         #endif
     }
 }