Attempt to cache using a temp file if home is unwriteable

[elldritch]

This helps alleviate #22 and #19, by attempting to use a temporary file to cache if the home directory is unwriteable. Previously, a temporary file was only used if the home directory could not be found.

[tkellen]

Thanks @ilikebits!

Can you add a passing test for this that fails without this addition?

[phated]

@tkellen isn't this similar to the patch that caused all the havoc not too long ago?

[elldritch]

@phated, that patch (#21) attempted to create new cache directories; this one fixes current cache behaviour to be as described. When $HOME is writeable, it behaviour is the same as it is now -- at the very least, I can't see this causing more problems.

@tkellen, working on tests now. There seem to be a couple of bugs with existing tests e.g. files written to temporary directories are not correctly cleaned up after each test because any invalid path passed to fs.unlinkSync or path.resolve will throw an error and prevent later (and possibly valid) paths from being removed. Is there any reason os is required at the test level instead of the file level?

[elldritch]

@tkellen Tests finished. I simulate an unwriteable $HOME by setting it to a non-existent directory.

[tkellen]

Thanks @ilikebits! This looks good to me. Can you please squash your commits? Also, if I give you commit and npm publish access for this repo, would you be willing to triage any issues that result?

[elldritch]

Sure thing; this bug blocks me from deploying on my PaaS provider, and I'd be happy to help out others with the same issue. I'm @ilikebits on npm as well.

[tkellen]

Sounds good @ilikebits! Matster is all set to npm publish the next version and you have author access on npm. Cut a release when ready :)

[tkellen]

Hey @ilikebits! Are you going to publish this?

[elldritch]

Sorry for the delay; it's finals crunch time right now, planning to release this weekend post-finals so I can address any bugs that come up.