Updating all pxt.microbit.org reference to makecode.microbit.org (#460)

clients/macuploader/Microbit Uploader/AppDelegate.m

@@ -124,7 +124,7 @@
 }
 
 - (void)launchEditor:(id)sender {
-    [[NSWorkspace sharedWorkspace] openURL:[NSURL URLWithString:@"https://pxt.microbit.org/"]];
+    [[NSWorkspace sharedWorkspace] openURL:[NSURL URLWithString:@"https://makecode.microbit.org/"]];
 }
 
 @end

clients/macuploader/README.md

@@ -3,10 +3,10 @@
 ![](Microbit Uploader/Assets.xcassets/AppIcon.appiconset/icon_256x256.png)
 
 This project is a clone of the [Windows
-uploader](https://pxt.microbit.org/uploader), but for OS X. Once launched,
+uploader](https://makecode.microbit.org/uploader), but for OS X. Once launched,
 the app runs in your menu bar and will automatically deploy any HEX files to
 your `@boardname@`. Like the Windows version, it is compatible with any browser
-that can run [pxt.microbit.org](http://pxt.microbit.org).
+that can run @homeurl@.
 
 ## Install the built version