Fix cache's file permission to 600

[Yuki-Inoue]

Since cache includes private information, (the auth-info), it's
permission should be set to 600.

[vermiculus]

Change looks good, thanks :) but it seems our tests need updating…

@Malabarba @jrblevin Has anything changed with markdown processing that could cause indented space after a code block?

i.e.,

[Malabarba]

We could probably just change our renderer to delete-trailing-whitespace after everything is done rendering.

[jrblevin]

I see that the text in the screenshot is from a test case. Should I think of it as pre-existing text that is fontified using markdown-mode, or is it being inserted and/or filled using markdown-mode functions? In other words, how does one reproduce this in a markdown-mode buffer?

[vermiculus]

I'm going to revamp the tests separately; we'll see how things fall after that.

[vermiculus]

I never did get around to revamping tests. Is this something that's still valuable to merge after all this time? Happy to do so if so.