Simplify FrameBuffer.

* Use _.compact when building the list of buffers in ``#consume.``
* Use the ``@buffer`` instance variable instead of passing it around.
* Inline ``dataSize`` into ``frameSize`` as it wasn't providing clarity.
* Inline ``unpackFrame`` into ``pluckFrame`` as it wasn't providing clarity.
* Remove the if/then from ``nextFrameOffset``, rename it to ``frameOffset``, reuse ``frameOffset``, and have the initial offset extraction while loop handle bounds checking.
* Use ``delete`` when losing the reference to ```@buffer``` instead of setting it to ```null```.
* Remove unnecessary parentheses.