If no path supplied ript barfs ugly

[gergnz]

When you don't supply a path, ript shows a ruby syntax error, instead of pretty usage, as what happens when you don't supply anything (see below).

gregc@dangermouse:~$ ript
Usage: /home/gregc/.rvm/gems/ruby-1.9.3-p374@ript/bin/ript <rulefile|directory>
gregc@dangermouse:~$ ript rules
Usage: /home/gregc/.rvm/gems/ruby-1.9.3-p374@ript/bin/ript <rules> <generate|diff|apply|save> <rulefile|directory>
gregc@dangermouse:~$ ript rules generate
/home/gregc/.rvm/gems/ruby-1.9.3-p374@ript/gems/ript-0.8.4/bin/ript:77:in `initialize': can't convert nil into String (TypeError)
    from /home/gregc/.rvm/gems/ruby-1.9.3-p374@ript/gems/ript-0.8.4/bin/ript:77:in `new'
    from /home/gregc/.rvm/gems/ruby-1.9.3-p374@ript/gems/ript-0.8.4/bin/ript:77:in `<top (required)>'
    from /home/gregc/.rvm/gems/ruby-1.9.3-p374@ript/bin/ript:19:in `load'
    from /home/gregc/.rvm/gems/ruby-1.9.3-p374@ript/bin/ript:19:in `<main>'
    from /home/gregc/.rvm/gems/ruby-1.9.3-p374@ript/bin/ruby_noexec_wrapper:14:in `eval'
    from /home/gregc/.rvm/gems/ruby-1.9.3-p374@ript/bin/ruby_noexec_wrapper:14:in `<main>'