Release 0.4

* Added more unit tests (#44, #45)
* Fixed consistency problems found with unit tests (#46)
* Packaged for PyPI:
  * Updated metadata
  * Store the version number inside the package, and add --version CLI option
  * Update README and convert to ReStructuredText, as required by PyPI

This release can be installed from the [PyPI test server](https://testpypi.python.org/pypi/openphoto):
```
   pip install -i https://testpypi.python.org/pypi openphoto
```
I'll upload it to the main PyPI site once this PR is merged.