Remade the code at tracker so it looks much cleaner.

Will start working at keeping peers, and not hammering the tracker
Changed local ip machine at udp request to 127.0.0.1
Added events on trackers

The client tells the tracker when download stops or completes.

Also govet-ed tracker , bitfield and bencode
Added choke and uninterested at peers

Also added peers mapping
Added peers management and changed requesting to trackers every 3.5 minutes

Also replaced dial with dialTCP because its way faster. Because of this speed doubled
Lots of refactoring and fixes
Incapsulated piece manager , added mutex inside piece_manager , deleted the one from downloader