Add a version exception for racket versions without scribble/example

[AlexKnauth]

What version of Racket are you using?

Racket version 6.3.

What should have happened?

I should be able to install fancy-app, as I could before commit 905f31c by @jackfirth.

This can be fixed by adding a version exception to the package server for racket versions 6.3 and below, pointing to commit 5743b26.

The versioned package source would be:

git://github.com/samth/fancy-app#5743b26

Or:

github://github.com/samth/fancy-app/5743b26

Or this if you want to create a new branch for it:

github://github.com/samth/fancy-app/for-version-up-to-6.3

[samth]

I'm not particularly worried about 6.3, since that was released quite a while ago.

[AlexKnauth]

It’s the first version with the scope-set macro expander, so it’s what I use to compare weird macros.

[AlexKnauth]

6.3 vs 6.2.1 I mean