Raw audio data as a `Source`

[agrathwohl]

Note: Raw media byte streams should be supported by Source however no Track class instance should be able to be made from them. A Source must be able to be decoded for it to derive any track instances.

A/C:

• raw boolean in the opts to indicate if the resource is raw audio
• ability to provide sample rate, bit depth, sampling format, etc. as a new opt (for use by sox later)