Document the name of RingBuf

[EdorianDark]

Currently the different collections are named after the implementation (RingBuf or BinaryHeap) and not the concept they implement (double ended queue or priority queue).

In some explanations of ring buffers (http://en.wikipedia.org/wiki/Circular_buffer) it is defined that adding elements to a full ring buffer leads to overwrite of elements. This seems not to be the case here.

Therefore I would suggest to change the introduction of the ring buffer documentation to:

RingBuf is a double- ended queue, which is implemented with the help of a growing circular buffer.