I think you're right about the issue tracker, but the wiki is just another git repo [1] that you can checkout, commit and push.
[1] https://help.github.com/articles/adding-and-editing-wiki-pag...
[1] https://help.github.com/articles/adding-and-editing-wiki-pag...
Hopefully gitlab or bitbucket comes up with a solution which enables the owners of the repos to move bugs/issue tracking, which will force github to enable this feature as well.
I like fossil because it's all built-in and can be wrapped up in a single file. But it's always great to have more choices available.