Sorted Containers

Added sorted containers to DataStructures, testing, and documentation.
Replaced README.md with README.rst
Since there is an enumerate function already in `Base`,

1. at a minimum, that function should be imported and "overridden" for the types you have here
2. you actually might not need these functions at all, since `enumerate` should just work with the standard iterators.  Your versions might be slightly more efficient, but if it isn't significant, I would propose removing them.