Upload support

This pull request introduces upload support. It does not come with documentation, as that will be part of a later pull request. If you wish to test uploading an archive: find any Python package, and run it's setup.py with the sdist argument. It will output a tarball, and you should be able to upload that to Pulp. To verify that it's been uploaded, you should be able to see it in Mongo like this:

```
> db.units_python_package.find()
```

Also, you should find the package you uploaded stored in ```/var/lib/pulp/content/python_package/```.
I don't dislike when others use that style, but I also have a purpose behind my style that I prefer. My tests take one code path each, rather than one assertion each. After the code path is taken, I make a variety of assertions about that code path. This helps reduce test code duplication since I don't have to take the same code path n times to make n assertions.

My test names usually are more meaningful than this one is, as they often indicate which code path they are supposed to target.