added CONTRIBUTING file with instructions for eventual contributors
added CONTRIBUTING file with instructions for eventual contributors

allcatsarebeautiful/tmux-mem-cpu-load,thewtex/tmux-mem-cpu-load,thewtex/tmux-mem-cpu-load,allcatsarebeautiful/tmux-mem-cpu-load,thewtex/tmux-mem-cpu-load,allcatsarebeautiful/tmux-mem-cpu-load,allcatsarebeautiful/tmux-mem-cpu-load,thewtex/tmux-mem-cpu-load