tmux: update tmux.conf for 2.1 version
tmux: update tmux.conf for 2.1 version

In version 2.1 some deprecated options were dropped and some options
changed names. So this is a quick fix to work in new version. Old
commands still left commented out.

rff/cfgbin,rff/cfgbin,rff/cfgbin,rff/cfgbin