DOC: Remove tips and tricks section page from the wiki
This page: https://github.com/pandas-dev/pandas/wiki/Tips-&-Tricks-for-pandas-dev is mostly outdated, or provides general Python information.

Personally, I'd just keep the last section on `PANDAS_TESTING_MODE`. Not sure if the best would be to move it to the CI part of the docs: https://pandas.io/docs/development/contributing.html#testing-with-continuous-integration

Or I'd probably just add a comment where that parameter is being used: https://github.com/pandas-dev/pandas/blob/master/.travis.yml#L46

Anything else that people would like to move to the docs from that page?