Remove (relative) line numbering.

  - On my 15" macbook I cannot see 2 windows side by side with 80chars
    per window when line numbering is on.  Without, it is possible and I
    can clearly see the column marker.

  - Although the relative line numbering seemed sweet, I don't use it
    nearly as much as I thought I would; the actions required take too
    long: look where you need to go, look at the gutter which relative
    line number that is and then <count>[k/j].
    Using '/' or '?' still seems to work quicker in most cases.