configurable tempdir

[daler]

I had to add this to allow the egs script to run on our cluster -- can't use /tmp from a node.

I didn't find any other examples of tempfile usage in this repo, but something to keep in mind is that it's useful to configure.

[landscape-bot]

Repository health decreased by 0.87% when pulling 1a87693 on daler:master into d73c52a on endrebak:master.

• 2 new problems were found (including 1 error and 1 code smell).
• No problems were fixed.