Fix rare bug where the takeWhileZero method would fail to repopulate the underlying buffer. This caused intermittent de-compression errors if takeWhileZero happened at a 64 bit boundary while the underlying buffer was empty.
The change also alters how sequence-lengths are encoded, to more consistently use the getGamma method instead of adding special significance to a zero first byte.
Finally, assertions are added checking the invariants of the gamma and delta coding logic as well as UrlIdCodec to earlier detect issues.
