Introduce Temporary.using for ensuring directory cleanup after use

Raised from Ivory [PR comment](https://github.com/ambiata/ivory/commit/79699cfcf8c80b77000865c8108036425249684c#commitcomment-6873287)

/cc @markhibberd @maxpow4h 
Not sure if it's dodgy/bad to use `Temporary` methods in other `Temporary` tests...