* Removed spurious override of convert method in map reduce demo
 * Throw exception and gave appropriate error message when closing resources in teardown for
   input and ouput operators
 * Handled edge cases for rolling files
 * Changed append property to define how files are treated when discovered by the operator. If
   the operator finds a previously unseen file and append is true, then that file is appended
   to. If the operator finds a previously unseen file and append is false, then that file is
   overwritten.
  * Fixed tests for single file writer.
 * Fixed test and imports
  * Fixed FSWindowWriter
  * Fixed improved tests for FSWindowWriter.