Fixed zero-contributor code

At present, the page will say "0 contributor" if there have been zero non-original-author contributors, when it should say "0 contributors". I have fixed this.

It may be worth looking at making it say something other than "and updated by 0 contributors" if it hasn't been updated by any contributors. In the mean time, however, "0 contributors" is a lot better than "0 contributor". 

JH