Fix several ruby warnings.
Fix several ruby warnings.

lib/mini_portile/mini_portile.rb:397: warning: assigned but unused variable - p_host
lib/mini_portile/mini_portile.rb:434: warning: assigned but unused variable - p_port
lib/mini_portile/mini_portile.rb:13: warning: method redefined; discarding old edit_path
lib/mini_portile/mini_portile.rb:82: warning: File.exists? is a deprecated name, use File.exist? instead

luislavena/mini_portile,jtarchie/mini_portile,luislavena/mini_portile,flavorjones/mini_portile,flavorjones/mini_portile