No support for different ports

[dehydr8]

Currently, only the default mysql port seems to be supported.

(line 57 of s3_mysql_backup.rb)

    `#{mysqldump} --host='#{config['dump_host']}' --user='#{config['dump_user']}' --password='#{config['dump_pass']}' '#{@db_name}' | gzip > #{filename}`

Please add support for different ports.

[fletchowns]

Maybe it should pass in any dump_* parameters to mysqldump automatically? That way every mysqldump parameter could be supported.