Linux client freezes X11 and crashes after run_keybase when an old keybase version is installed

Had an old version of keybase installed (0.7.7) and followed these instructions:

```
curl -O https://prerelease.keybase.io/keybase_amd64.deb
sudo dpkg -i keybase_amd64.deb
sudo apt-get install -f
run_keybase
```

Got the top part of this output http://imgur.com/a/jMlay (ending in the squirrel) and sometimes a Keybase GUI window would appear, but then X11 would freeze and I had to Ctrl+Alt+F1 and `killall Keybase` in order to get X11 back (and then all the X errors followed in the terminal.)

I couldn't find any documentation online but with the help of archive.org I eventually ran `sudo npm uninstall -g keybase` and then was able to install properly according to the instructions. Might be helpful to handle this case more gracefully.

Start by reproducing the documented curl, dpkg, apt-get, and run_keybase sequence with an old 0.7.7 installation, then inspect the client and installation entry points involved in startup. The report names no repository files or tests; done means avoiding the X11 freeze and handling the old installation case gracefully.

Written by the indexing model from the issue text.