DOC: Remove and disable wiki
I've been having a look at the pages on the GitHub wiki, and I think the content is mostly outdated, not very useful, and in some cases opinionated and not specific to pandas.

Not sure if there is anything worth keeping. But if there is, its not much, and I think it should be moved to the docs, so it's more visible, and we can open PRs on it, to update or delete the content.

Once the content we want to keep is in the docs, I'd diable the wiki. Personally I don't see any use case for it in our l project. The docs can contain everything. 

Any objection? Anything that someone wants to keep? 