Issue

Description

As reported in Gitter by user @evilblade666

`Hi, guys. My home

After 6 months my cache folder has grown to 78GB. Perhaps old transcoded files should be deleted?

Currently the files esmBot puts in TEMPDIR are not pruned by the bot. It's possible for people running the bot to prune the folder through other means, on the live bot they are pruned through a cronjob. It'd be better for this to be baked into esmBot itself.

esmBot should have be a THRESHOLD env option. Whenever TEMPDIR's file sizes total more than THRESHOLD bytes, esmBot will delete files,