resolve #3 [rt.cpan.org #70609] - load order tweak

delay the call to FCGI::Request until the first call to ->new to
remove the need to have the ENV variables set in a BEGIN block in
the calling script

add import options for those ENV variables as socket_path and
listen_queue so they can be set at module use rather than ENV
settings, which is somewhat cleaner. however if the ENV variables
are set then favour those

update documentation to reflect above changes, as well as some
general cleanup to the perldoc