Borgmatic

* 57: When generating sample configuration with generate-borgmatic-config, comment out all
optional configuration so as to streamline the initial configuration process.

* Fix for archive checking traceback due to parameter mismatch.

* 64, 90, 92: Rewrite of logging system. Now verbosity flags passed to Borg are derived from
borgmatic's log level. Note that the output of borgmatic might slightly change.
* Part of 80: Support for Borg create --read-special via "read_special" option in borgmatic's
location configuration.
* 87: Support for Borg create --checkpoint-interval via "checkpoint_interval" option in
borgmatic's storage configuration.
* 88: Fix declared pykwalify compatibility version range in setup.py to prevent use of ancient
versions of pykwalify with large version numbers.
* 89: Pass --show-rc option to Borg when at highest verbosity level.
* 94: Support for Borg --json option via borgmatic command-line to --create archives.

* 85: Fix compatibility issue between pykwalify and ruamel.yaml 0.15.52, which manifested in
borgmatic as a pykwalify RuleError.

* Skip before/after backup hooks when only doing --prune, --check, --list, and/or --info.
* 71: Support for XDG_CONFIG_HOME environment variable for specifying alternate user ~/.config/
path.
* 74, 83: Support for Borg --json option via borgmatic command-line to --list archives or show
archive --info in JSON format, ideal for programmatic consumption.
* 38, 76: Upgrade ruamel.yaml compatibility version range and fix support for Python 3.7.
* 77: Skip non-"*.yaml" config filenames in /etc/borgmatic.d/ so as not to parse backup files,
editor swap files, etc.
* 81: Document user-defined hooks run before/after backup, or on error.
* Add code style guidelines to the documentation.

* 61: Support for Borg --list option via borgmatic command-line to list all archives.
* 61: Support for Borg --info option via borgmatic command-line to display summary information.
* 62: Update README to mention other ways of installing borgmatic.
* Support for Borg --prefix option for consistency checks via "prefix" option in borgmatic's
consistency configuration.
* Add introductory screencast link to documentation.
* 59: Ignore "check_last" and consistency "prefix" when "archives" not in consistency checks.
* 60: Add "Persistent" flag to systemd timer example.
* 63: Support for Borg --nobsdflags option to skip recording bsdflags (e.g. NODUMP, IMMUTABLE) in
archive.
* 69: Support for Borg prune --umask option using value of existing "umask" option in borgmatic's
storage configuration.
* Update tox.ini to only assume Python 3.x instead of Python 3.4 specifically.
* Add ~/.config/borgmatic/config.yaml to default configuration path probing.
* Document how to develop on and contribute to borgmatic.