Move files into a format suitable for distributing on PyPI.

Hey there @picklepete -- I came across your project just a little while ago while investigating how I might integrate some iCloud functionality into a web app of my own, and couldn't help but notice that the package wasn't currently distributed on PyPI.  This PR will move the files in this repo around into a format usable by `setuptools` for packaging and distribution.

Upon merging in these changes, you can upload this package to PyPI so users may easily install the package by running:

```
python setup.py sdist register
```

to register your package on PyPI, then

```
python setup.py sdist upload
```

to upload the current version of your package to PyPI.

In addition to the packaging changes, I also fixed the login process -- the endpoint you were initially connecting to for populating `clientBuildNumber` no longer exists.

Thanks for your code!