Feat
- **git**: get_commits default from first_commit
Refactor
- **commands/bump**: rename parameter into bump_setting to distinguish bump_setting and argument
- **git**: rename get tag function to distinguish return str and GitTag
- **cmd**: reimplement how cmd is run
- **git**: Use GitCommit, GitTag object to store commit and git information
- **git**: make arguments other then start and end in get_commit keyword arguments
- **git**: Change get_commits into returning commits instead of lines of messages