Hadoop DFS 'TmpDir Cleanup' support

* Renamed $HADUPILS_BASE_TMP_PATH to $HADUPILS_TMP_PATH (less typing)
* Introduced $HADUPILS_TMP_TTL for use with command: cleanup
* Introduced Hadupils::Commands::Cleanup to identify and remove old
  hadupils tmp DFS directories/files where all files within any
  hadupils-tmpdir* in $HADUPILS_TMP_PATH are older than
  $HADUPILS_TMP_TTL, the TTL (Time.now.utc - $HADUPILS_TMP_TTL)
* The Hadupils::Runnders::Base.new.execute! method now uses
  Open3.capture2 or Kernel.system
* Fixed 1.8.7 compatibility bug with the Kernel.system call in
  Hadupils::Extensions::Hive::AuxJarsPath.build_archive
* Some code and unit test refactoring
* Bumped version to 0.6.0