Chronophore

Added
- There are now two scripts that allow you to convert any of Chronophore's data files between xlsx and json.
- These conversion scripts have a '--clobber' option, which allows them to overwrite existing files. By default, this is prevented.
- Added a script to generate sample sign-in data.
- Chronophore is now on [pypi](https://pypi.python.org/pypi/chronophore/0.2.0)! It can be installed with `pip3 install chronophore`.

Changed
- Impoved and simplified the way data is represented internally.
- Improved error handling.

The first release of chronophore.

Features
- Basic functionality is in place:
- User sign-in and sign-out
- Store data in json files
- Check that user is in users.json
- Tk gui
- Input and file validation
- Error logging

Windows executable made with [PyInstaller](http://www.pyinstaller.org/).
Requires 64-bit Windows 7