Removed unnecessary src folder

Since there is only one package and the common practice is to have this in the root folder. This saves a lot of unnecessary typing.
Factor XPath extraction into Feed.

It is very confusing and adds unnecessary complexity to have three mixins for several types of XPath extraction.

The original path to make these pluggable features has been left some time ago.
Some enclosure URL's are really huge
Disable south migrations in tests
Test coverage for utility methods.