Closing a TextEditor wipes all messages for that file

[Arcanemagus]

When you close a TextEditor instance it seems that linter is removing all messages associated with that TextEditor which is great if that was the only instance of that file open.

If however there are multiple TextEditors open to a single file (TextBuffer), then the messages are cleared on the other TextEditors and need another lint() call to recreate them.

Steps to reproduce:

1. Open a file, create some linter messages in it
2. Split the file into multiple editors
3. Close the second one of them

Expected:
The first instance on the file still shows the same messages it did before the second instance was closed.

Actual:
The messages are cleared from the first instance, requiring lint to re-run to recreate them.

Seen with:

• linter-ui-default
• linter-ui-plus
• atom-minimap-linter

[steelbrain]

This has been fixed in master