rebased version of doclit.py, eseentially v 0.0.1

hi - hope you remember me.
I am slowing catching up on the "Big List Of Things Todo" and have even gone and added a extra to doctest

1. doctest now sits in a directory-structurted package
2. added sphinx docs v. rough ready
3. added "doclit"

doclit - basically lets you write a doctest file, with say a function in the file.
Then you write a second doctest file and "import" the first .txt file into the doctest namespace and hey presto - you can write a book and build on exmaples from first chapter in the subsequent ones.