Support :Port as string

[iconara]

This patch fixes an issue with running rackup --port 3333. For some reason rackup doesn't convert the argument to an int before passing it to the handler, and currently Jubilee's RubyServer expects this option to be numeric.

An example:

% cd spec/apps/rack/basic
% ruby -I ../../../../lib -S rackup -s jubilee --port 3333
TypeError: can't convert String into Integer
  initialize at org/jruby/jubilee/RubyServer.java:69
  initialize at /Users/theo/Documents/Code/jubilee/lib/jubilee/server.rb:9
         run at /Users/theo/Documents/Code/jubilee/lib/rack/handler/jubilee.rb:24
       start at /Users/theo/.rvm/gems/jruby-1.7.8@jubilee/gems/rack-1.5.2/lib/rack/server.rb:264
       start at /Users/theo/.rvm/gems/jruby-1.7.8@jubilee/gems/rack-1.5.2/lib/rack/server.rb:141
      (root) at /Users/theo/.rvm/gems/jruby-1.7.8@jubilee/gems/rack-1.5.2/bin/rackup:4
        load at org/jruby/RubyKernel.java:1103
      (root) at /Users/theo/.rvm/gems/jruby-1.7.8@jubilee/bin/rackup:23

But with this patch it starts nicely.

Thanks for Jubilee, I like it a lot. I hope I can help out along the way.

[isaiah]

And welcome on board :+1: