Simbak

- Hotfix, added dependent package (`python-dotenv`) to the installation.

- Improved logging once again.
- Added a Rotating Agent. This agent will do rotating backups up to a
"rotate limit" once the rotate limit is exceeded, it will remove the
oldest backup of that specified rotating backup spec.
- Plenty of housekeeping and bug fixes.

- Improved logging messages slightly.
- Will now log messages to files to the following locations.
- Windows `%APPDATA%\simbak\` or `C:\Program Data\simbak\`
- Linux `/var/log/simbak/`

- Removed `simbak/backup.py` module.
- It contained only one public method `simbak.backup.backup()`, and
wasn’t able to scale well.
- Moved the one public method to `simbak/__init__.py` so that the
method signature is smaller `simbak.backup()`
- This can be the one and only quick backup method to use, which
will perform a standard backup. It should meet the needs for most
people, and keeps it simple. Other more complex backup solutions
will be in the new `simbak/backup` package.
- There are now backup 'agents', which will perform different backups,
for now there is only a `NormalAgent`.
- Added unit tests.

- Critical error with logging fixed, logging should now work normally.

- Improved logging.
- Added messages to make it more clear what simbak is doing.
- Log files are now stored.
- Established that we are using semantic versioning.