fix ftp_port

Hi,

This fixes the ftp storage adapter to correctly pass the ftp_port to Net::FTP.  Currently it passes the ftp_port as the last arg to open, which is supposed to be acct:

http://ruby-doc.org/stdlib-2.0.0/libdoc/net/ftp/rdoc/Net/FTP.html#method-c-open

I've fixed this to use connect.  see #19 for the test