Making it compatible with Whonix

https://github.com/NullHypothesis/exitmap/issues/56:

Right now it's not possible to run exitmap in Whonix,

2017-03-13 12:43:09,944 exitmap [INFO] Attempting to invoke Tor process
in directory "/tmp/exitmap_tor_datadir-user".  This might take a while.
2017-03-13 12:43:09,944 exitmap [INFO] No first hop given.  Using
randomly determined first hops for circuits.
2017-03-13 12:43:09,982 exitmap [ERROR] Couldn't launch Tor: Process
terminated: Timed out.  Maybe try again?