public static byte[][] split(final byte[] a, final byte[] b, final int num) {
    return split(a, b, false, num);
  }
Split passed range. Expensive operation relatively. Uses BigInteger math. Useful splitting
ranges for MapReduce jobs.
@param a   Beginning of range
@param b   End of range
@param num Number of times to split range. Pass 1 if you want to split the range in two; i.e.
           one split.
@return Array of dividing values
hbase-common/src/main/java/org/apache/hadoop/hbase/util/Bytes.java