PARQUET-1561: Inconsistencies in the Delta Encoding specification (#128)
PARQUET-1561: Inconsistencies in the Delta Encoding specification (#128)

* Addressed most points in PARQUET-1561. We should add examples containing
multiple miniblocks and blocks.

* Defined ULEB128 and zigzag encoding.

* Padding bits and bytes should be zero, but readers should not rely on it.

apache/parquet-format,apache/parquet-format,apache/parquet-format