CircularBuffer: use vector instead of allocating memory ourselves
CircularBuffer user cares about working set size

Capacity (size of actual buffer) is an implementation detail
CircularBuffer: support working set of size 0 (no-op)
CircularBuffer: use const_iterator for gmock

Test container elements using ASSERT_THAT.

Don't need non-const iterator for any other use cases at the
moment. Gmock needs a const_iterator to test the elements in a
container.
CircularBuffer: hack for gtest to think we're a container
Clean up CircularBuffer algorithm
CircularBuffer: expand
CircularBuffer: support shrinking
CircularBuffer: shrink->expand seems to work

Need more testing.
Support starting from size 0 and expanding
CircularBuffer: Remove test coverage markers
CircularBuffer: clean up dead code
CircularBuffer: resize call
Window resizes are now handled in a nice way

We will always make use of all the space we have!