Fix #228 introduced by variable length encoding where integer values stored on
single bytes in HBase were being cast to unsigned ints in
RowSeq.extractIntegerValue. Removed the bitmask and now single bytes are
returned correctly.

Signed-off-by: Chris Larsen <clarsen@euphoriaaudio.com>
Add unit tests for writing negative values and VLE integers through TSDB

Signed-off-by: Chris Larsen <clarsen@euphoriaaudio.com>