Fix several instances of 'Method may fail to close stream' within gora-accumulo BinaryEncoder

A number of methods within the BinaryEncoder class create an IO stream object, does not assign it to any fields, pass it to other methods that might close it, or return it, and does not appear to close the stream on all paths out of the method. This may result in a file descriptor leak. It is generally a good idea to use a finally block to ensure that streams are closed.