Borgmatic

* Part of 125: Color borgmatic (but not Borg) output when using an interactive terminal.
* 166: Run tests for all installed versions of Python.
* 168: Update README with continuous integration badge.
* 169: Automatically sort Python imports in code.
* Document installing borgmatic with pip install --user instead of a system Python install.
* Get more reproducible builds by pinning the versions of pip and tox used to run tests.
* Factor out build/test configuration from tox.ini file.

* Add validate-borgmatic-config command, useful for validating borgmatic config generated by
configuration management or even edited by hand.

* 160: Fix for hooks executing when using --dry-run. Now hooks are skipped during a dry run.

* 155: Fix for invalid JSON output when using multiple borgmatic configuration files.
* 157: Fix for seemingly random filename ordering when running through a directory of
configuration files.
* Fix for empty JSON output when using --create --json.
* Now capturing Borg output only when --json flag is used. Previously, borgmatic delayed Borg
output even without the --json flag.

* 148: Configuration file includes and merging via "!include" tag to support reuse of common
options across configuration files.

* 147: Support for Borg create/extract --numeric-owner flag via "numeric_owner" option in
borgmatic's location section.