Render .wiki pages in source view also.

Render all wiki pages in the main repo (not the BitBucket repo Wiki) in MediaWiki format just like .md files are also rendered in the source view, and not just in the readme.md view.

In other words, currently .md files in the source view are rendered, but .wiki files are not.

The call is to enable rendering for repo wiki pages in the source view.

Alternatively you could also enable a configuration switch for changing this rendering to Creole syntax or to lobby with GitHub to enable it for theirs . Creole seem to be preferable to Mediawiki, but in the aspect of interoperability and portability, main repo wiki pages should just all render in MediaWiki for now.