Build-magic

* Fixed a cleanup action bug that prevented existing empty directories from being deleted.
* Updated paramiko to 2.10.1.

* Added the --skip switch to manually skip named stages.
* Added the current working directory to stdout.
* Fixed a regression bug that caused the bind and hostwd parameters to fail validation.
* Fixed a bug introduced in 0.4.1 that would delete existing directories when the cleanup action was used.

* Updated python packages.
* Fixed a cleanup action bug on Windows that prevented directories mis-identified as files from preventing cleanup.
* Fixed a cleanup action bug that prevented files in an empty working directory from being cleaned up.
* Fixed a cleanup action bug that prevented an empty directory from being deleted.
* Fixed a bug that would raise an unhandled exception if a Windows path was provided as a runtime variable.
* Fixed a cleanup action bug on Windows with the remote command runner.

* Added a prep section to config files.
* Added author, maintainer, version, created, and modified sections to config files.
* Added the --info option to the CLI for viewing config file meta data.
* Added dotenv file support.
* Added support for environment variables.
* Added support for command labels to optionally display instead of the command itself.
* Added support for job and stage descriptions.
* An environment can now be specified for the Local command runner and the stage will be skipped if the environment doesn't match the current OS or distribution.
* Build-magic creates and uses a custom Vagrantfile when using the Vagrant command runner and setting bind directory or envvars.
* Bugfixes

* Fixed a bug where an error when parsing a YAML file was not caught and handled.
* Code cleanup and style enforcement with Flake8.

* Updated dependencies to newer versions.