Install and use keybase as a user without root

Steps to reporoduce:
1. Run the curl script and get the deb file.
2. dpkg to get the files
3. add {base-folder}/usr/bin to path

4. try run_keybase and fail

```
$ run_keybase
Starting via systemd...
Failed to restart keybase.service: Unit keybase.service not found.
```

5. try keybase login and fail

```
keybase login
▶ INFO Starting keybase.service.
Failed to restart keybase.service: Unit keybase.service not found.
▶ ERROR Failed to start keybase.service.
▶ ERROR Error in spawning server process: exit status 5
▶ ERROR exit status 5
```

6. (Optional) Create an issue on the github repo

Start by reproducing the curl, dpkg, PATH, run_keybase, and keybase login steps described in the issue. Investigate how the user-level installation is expected to start keybase.service; done means the client can start and log in without root or a system-wide service installation.

Written by the indexing model from the issue text.