Fix failure to import into directory journal

[micahellison]

Fixes #999.

A couple issues were at fault:

• the FolderJournal only writes entries with the "modified" property set to True. However, imported entries weren't marked as "modified"
• the FolderJournal writing method wasn't identifying new ("modified") dates appropriately

There are some larger issues with this whole object model, mainly that it's not really hiding complexity. Whether you're calling or inheriting a Journal, you've got to know how its innards work, and that makes it difficult to extend. But first and foremost, I wanted to get this bug fixed.

Checklist

• I have read the contributing doc.
• I have included a link to the relevant issue number.
• I have tested this code locally.
• I have checked to ensure there aren't other open pull requests
  for the same issue.
• I have written new tests for these changes, as needed.
• All tests pass.

[wren]

📦

[viegasfh]

Regarding this issue, I would to add that even though the import wasn't working in the command line, there is a workaround:

1. Do a jrnl nameofjournal --edit (or -n 1 --edit) to edit in your text editor
2. Paste the entries from the text based journal (in vim do an insert text file)
3. Save and exit

After you save, you will find a message like the following:

[-44 entries deleted, 44 entry modified]

I don't know why it says -44 entries deleted, because it had none of them before. So, it should only say 44 entries added.

Doing a jrnl nameofjournal --export pretty, shows all the entries.

So, maybe this fix could also improve the message displayed so that it says the correct thing in cases where we paste the entries directly in the editor.