Chunksize can be calculated without needing an ALSA device instance.
Added a DataSize function to pcm package for calculating size of pcm data given relevant attributes.
Removed ChunkSize from config revid config struct.
Changed NewByteLexer to accept an in rather than a pointer.
av/device/device.go now contains the AVDevice interface and implementations of this
interface, namely, raspivid, geovision, webcam and file are contained in the packages
av/device/raspivid, av/device/geovision, av/device/webcam and av/device/file
respctively. config.go and testing was also moved to a new package called config.go in
order to remove would be circular dependency between AVDevice implementations and revid.
Modifications were made elsewhere expecting config.Config to be part of the revid package.
Frank Cui