Python-dotenv

- Add `--version` parameter to cli ([venthur])
- Enable loading from current directory ([cjauvin])
- Add 'dotenv run' command for calling arbitrary shell script with .env ([venthur])

- Add tests for docs ([Flimm])
- Make 'cli' support optional. Use `pip install python-dotenv[cli]`. ([theskumar])

- `set_key` and `unset_key` only modified the affected file instead of
parsing and re-writing file, this causes comments and other file
entact as it is.
- Add support for `export` prefix in the line.
- Internal refractoring ([theskumar])
- Allow `load_dotenv` and `dotenv_values` to work with `StringIO())` ([alanjds])([theskumar])([78])

- Remove hard dependency on iPython ([theskumar])

- Add support to override system environment variable via .env.
([milonimrod](https://github.com/milonimrod))
([\63](https://github.com/theskumar/python-dotenv/issues/63))
- Disable ".env not found" warning by default
([maxkoryukov](https://github.com/maxkoryukov))
([\57](https://github.com/theskumar/python-dotenv/issues/57))

- Add support for special characters `\`.
([pjona](https://github.com/pjona))
([\60](https://github.com/theskumar/python-dotenv/issues/60))