* Add save_db()
* Refine test code
Add backup methods.
Fix typo.
Merge pull request #14 from imZack/develop

Add vaildation and refine tests
Merge remote-tracking branch 'upstream/develop' into develop
Add backup thread to backup db every x hours.
fix: E265 block comment should start with '# '
Merge pull request #15 from ckgczarzar/develop

Add db's backup method.
Add voluptuous in setup.py