Resolves #79. When tmux is compiled from source the version string is "master" which the tmux-version command didn't deal with correctly.
When using Tmux 1.9 and later the "-c" argument is given to the "new-session" command to set the session's root/default path. When using Tmux 1.8.x and earlier, the old "default-path" session option method is used instead.