link to episode on hosting

In the remotes section we say we'll review the pros/cons of hosting services in a later episode.  This PR adds the link to that later episode.

episodes/07-github.md

@@ -26,7 +26,7 @@ practice, though, it's easiest to use one copy as a central hub, and to keep it
 on the web rather than on someone's laptop.  Most programmers use hosting
 services like [GitHub](https://github.com), [Bitbucket](https://bitbucket.org) or
 [GitLab](https://gitlab.com/) to hold those main copies; we'll explore the pros
-and cons of this in a later episode.
+and cons of this in a [later episode](13-hosting.html).
 
 Let's start by sharing the changes we've made to our current project with the
 world. To this end we are going to create a *remote* repository that will be linked to our *local* repository.