Merge pull request #31 from psaab/develop

Introduce TorrentSize stat and replace some locks in PeerMap with atomic increments.
Merge pull request #32 from psaab/develop

Limit number of concurrent connections
Go routine stat
go fmt [ci skip]
Use signed ints for current counts
Fix IPv4 stats

net.ParseIP() will return a v4mapped address which makes len(ip) ==
IPv6len and breaks stats for IPv4 requests.