- Moved Archive class into separate python file.

- Updated ArchiveMain.py to use new Archiver.py file.

- Create ArchiveTest.py for automated tests.

- Added some automated tests for the Archive class to test:
  - Can open a .zip, .rar, .tar, .tar.gz and tar.bz2 archive.
  - Can write a single file to a zip archive.
  - Can recognize if a file is a .zip, .rar, .tar, .tar.gz and tar.bz2 archive.

- Modified rarfile.py to fix warning about file not being closed when
  calling rar_file.is_rarfile.

- Renamed "test archives" folder to test_archives to make it easier to use
  with the command line.