Updated gloom-style game list

-Tremulous has not had development for quite a while
-Trem/Unvanquished are not natural selection inspired.  They derive from gloom (http://www.moddb.com/mods/gloom) which was developed around the same time as ns1, but was not derived from ns1.
Merge pull request #59 from Forty-Bot/patch-1

Updated gloom-style game list