#84 Installer Should Clean Up After Itself

[chromatic]

The installer leaves behind relics of failed
installations. This is evident in two places. First,
it creates dummy databases and does not remove them.
Second, it unpacks nodeballs to directories under /tmp
and does not remove them.

I suggest adding an END block to clean up the dummy
database.

We ought to use File::Temp to handle the nodeball
unpacking. It is a core module and it cleans up after
itself handily.