Documenting new features and bug fixes

Release Notes

When adding a new feature or fixing a bug, it is much appreciated to document what you did with a compact reference in the release notes for that version, in doc/source.releast.rst. Please reference the issue or pull request you can do it like so: :issue:`12345` where 12345 is the issue/pull request number.

Whatsnew

In addition, if the feature/improvement is noteworthy, please document it in the appropriate section in the whatsnew in a few lines or less in doc/source/vX.Y.Z.txt where X, Y, Z form the current development version of pandas.