Dmenu compatible options

[Cloudef]

Getopts does not support the dmenu's single dash longopts, we should only support the dmenu opts with single dash. Preprocess those before getopts perhaps.

[avalonwilliams]

A simpler solution than changing the code could possibly be to distribute an (optional) shell script that allows bemenu to be used as a drop-in replacement for dmenu. Though, I do realize this may cause some issues with package management, as well as cross-platform compatibility potentially.

I've written a script to do this for personal use, though it relies on bash.