pre major refactor

remove Rakefile;  replace with Makefile
change LICENSE to GPL 3
remove Travis CI;  replace with github workflow
target sourcemod versions 1.10, 1.11
update include files to use new syntax
update .gitignore
remove tabs
fix warnings/errors for sm-1.10
fix for game description showing Shootout instead of Gun Game
fix off by one check with MaxClients
Add a useful README.md
rename main script to standard gungame_fof.sp