Support configfile in current directory. Working from the
root of a Rails project, its tmuxinator configuration can
be stored at that root, enabling it to be packaged with
the project's source tree. Starting tmux with no arguments
will launch the default 'tmuxinator.yml' from the current
directory if that exists. If a project name is given and
its file exists in the current directory it will be used
in preference to anything in ~/.tmuxinator.

Note: nothing has been done to facilitate writing configs
to the current directory: they can be created as normal
in ~/.tmuxinator and copied manually. Further editing can
always be done directly using vim.