Shell Features, Plugin Improvements, Docker Support, and Book Progress in Nushell

We've made steady progress on improving error messages. Recently, we added "did you mean?" errors to help when you mistype the name of columns. Nu 0.3.0 also has gone through a few passes to generally polish the errors to include more information when an error occurs. ## Shell features (pka, wycats, twe4ked, andrasio, iamcodemaker) Nu now supports `~` to refer to your home directory as part of a path. You can also use `cd -` to return to a previous directory you were working in. The shell itself also got a few updates. You can now enable 'vi' mode, if you'd prefer vi-like bindings (by running `config --set [edit_mode vi]`). On non-Windows platforms, you can also use Ctrl-R to enable Sublime-style history searching (we're hoping to enable Windows support for this soon). ## Plugin improvements (sophiajt, andrasio) Plugins have continued to mature, and it's now possible to use plugins to extend Nu with support for new file formats. We've also added documentation on how to [write Nu plugins in both Rust and Python](https://github.com/nushell/contributor-book/blob/master/en/plugins.md), with info on Ruby coming soon. ## Docker support (vsoch, DrSensor) If you're interested in using Nu and Docker together, be sure to check out the [new Docker support](https://github.com/nushell/nushell/blob/master/docs/docker.md). ## Book progress The [Nu book](http://book.nushell.sh) is now available in _three_ languages: English, Spanish, and Japanese. We've also created a [Nu contributor book](https://github.com/nushell/contributor-book/blob/master/en/README.md), which will help developers who want to contribute to Nu learn about its philosophy, design, and how to create plugins. ## Acknowledgements est31, pmeredit, twe4ked, DrSensor, vsoch, pka, jankoprowski, Porges, max-sixty, ijt, djc, vthriller, taiki-e, oskarskog, iamcodemaker, JonnyWalker81, yaahc, tim77, svartalf, ramonsnir, orf, lesichkovm, ineol, incrop, eoinkelly, devnought, chhetripradeep, aidanharris, GuillaumeGomez, and BatmanAod for contributing to the Nu codebase. Also a _big_ thanks to our issue reporters! ymgyt - for the Japanese version of the Nu book! mistydemeo, romanlevin, ralvessa, pka, lord, kkalyan, jankprowski, and boisgera for helping with the book. ## Looking ahead We're hard at work on the [upcoming milestone release](https://github.com/nushell/nushell/issues/261). If you'd like to help, feel free to jump in! We have an active [discord](https://discord.gg/NtAbbGn) you can join for both users and contributors.

Nushell now supports `~` for home directories and `cd -` for previous directories. It also supports 'vi' mode and Sublime-style history searching (on non-Windows platforms). Plugins have been improved, and documentation on writing Nu plugins in Rust and Python has been added. Docker support has been added, and the Nu book is now available in English, Spanish, and Japanese. There's also a Nu contributor book to help developers contribute to Nu.