Use BytesStringer instead of ZeroCopyByteString

Since HBASE-11118 (0.98.4, 1.0), we should be using the utility class ByteStringer instead of HBaseZeroCopyByteString. Using HZCBS requires the user to include hbase-protocol.jar in their HADOOP_CLASSPATH. HBASE-11118 removed this requirement, and enables environments like Oozie and Cascading's tools.