Changelog
- Add `python-dateutil` and `retry_requests` to the dependency list.
- rename `highlights` flag to `summary`
- show the date on which the summary or stat was generated.
- validate user input for custom summary durations and GitHub username and show appropriate errors.
**[Commits from v0.0.1 to v0.0.2](https://github.com/interviewstreet/ghs/compare/v0.0.1...v0.0.2)**