#239 #248 Hopefully fixes the BufferOverflowException by growing the internal ByteBuffer by lengthFieldLength.

Also adds support for short (2) as a lengthFieldLength.
Minor typo fix.
The exposesNettyByteBuf() test must use a SynchronousDispatcher since we're reading from the Netty ByteBuf directly. That must take place in Netty's IO event loop thread and not in some other thread, which causes random failures due to doing out-of-band IO in reading from Netty's buffer.