Nu Shell Updates - Week #42

1st chunk of `blog/2020-06-12-twin0042.md`

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# This week in Nu #42

- utam0k added an option to `mkdir` to [show the paths being created](https://github.com/nushell/nushell/pull/1932)
- JosephTLyons [removed async_stream from some commands](https://github.com/nushell/nushell/pull/1940) ([2](https://github.com/nushell/nushell/pull/1951)), fixed [spaces in test paths](https://github.com/nushell/nushell/pull/1944), [updated `cal`](https://github.com/nushell/nushell/pull/1945),
- samhedin added support for [per-directory environment variables](https://github.com/nushell/nushell/pull/1943)
- arashout improved `to toml` to [disallow top-level values](https://github.com/nushell/nushell/pull/1946)
- daschl made [interruptible streams public](https://github.com/nushell/nushell/pull/1952)
- jonathandturner renamed the ".env" file to [".nu-env"](https://github.com/nushell/nushell/pull/1953), [released 0.15.0](https://github.com/nushell/nushell/pull/1955), fixed a bug with [operator precedence](https://github.com/nushell/nushell/pull/1966), add support for [readonly config files](https://github.com/nushell/nushell/pull/1967), and move a [batch of commands off async_stream](https://github.com/nushell/nushell/pull/1970)
- svartalf fixed an issue with process usage and [bumped the heim dependency](https://github.com/nushell/nushell/pull/1954)

Also!

- We've added our [initial RFC process](https://github.com/nushell/rfcs). Come let us know what you think.

Title: Nu Shell Updates - Week #42

Summary

This week in Nu shell saw several updates and fixes including: mkdir path display option, removal of async_stream from some commands, per-directory environment variables, TOML improvements, interruptible stream publicizing, .env file rename to .nu-env, version 0.15.0 release, bug fixes, readonly config file support, and heim dependency update. Additionally, the initial RFC process has been added.