Issue #264: test test_bake_archive__known fails when zip is not installed (blais/beancount)

[Martin Michlmayr]

New issue 264: test test_bake_archive__known fails when zip is not installed
https://bitbucket.org/blais/beancount/issues/264/test-test_bake_archive__known-fails-when

Martin Michlmayr:

test_bake_archive__known relies on `zip` (and `tar`):

```
ERROR: test_bake_archive__known (beancount.scripts.bake_test.TestScriptArchive)
----------------------------------------------------------------------
Traceback (most recent call last):
File "/home/tbm/beancount/beancount/utils/test_utils.py", line 228, in new_function
return function(self, file.name)
File "/home/tbm/beancount/beancount/scripts/bake_test.py", line 248, in test_bake_archive__known
self.get_args() + [filename, outfile])
File "/home/tbm/beancount/beancount/utils/test_utils.py", line 95, in run_with_args
return function()
File "/home/tbm/beancount/beancount/scripts/bake.py", line 262, in main
archive(archival_command, output_directory, opts.output, True)
File "/home/tbm/beancount/beancount/scripts/bake.py", line 189, in archive
stderr=subprocess.PIPE if quiet else None)
File "/usr/lib/python3.6/subprocess.py", line 709, in __init__
restore_signals, start_new_session)
File "/usr/lib/python3.6/subprocess.py", line 1344, in _execute_child
raise child_exception_type(errno_num, err_msg, err_filename)
FileNotFoundError: [Errno 2] No such file or directory: 'zip': 'zip'
```

This is documentation issue. You need zip and tar (bean bake) and gnupg (for encryption).