ubuntulinux.md - old commands, typo, section movement

- Removed some commands related to autocomplete/symlinks that don't seem to be required anymore on Ubuntu 14.04
- Fixed one minor typo ("see LINK _for_ details," not "see LINK details")
- Moved section "Giving non-root access" to top level, rather than being under Ubuntu 13 (the section isn't specific to Ubuntu 13, and even references Ubuntu 14).

Signed-off-by: Scott Walls <sawalls@umich.edu>
Merge pull request #8837 from sawalls/patch-2

ubuntulinux.md - old commands, typo, section movement