verify behavior for:
- current version (no change)
- old, supported version (upgrade, but not too far)
- too old, re-run installer
- directory exists, no conda
- When processes fail, they actually print a failure message
on the user's terminal
- Regardless of success or failure, we print all output to
/opt/tljh/installer.log
This should make debugging people's issues *much* easier, since
we can actually see the output of failing commands rather than
having to guess.
