Set SendEpoch instead of cumulating it (#86)

`CalculateNextEpoch` should set `SendEpoch` instead of cumulating it.

README.md

@@ -8,7 +8,7 @@ https://camo.githubusercontent.com/915b7be44ada53c290eb157634330494ebe3e30a/6874
 [![Go Report Card](https://goreportcard.com/badge/github.com/vacp2p/mvds)](https://goreportcard.com/report/github.com/vacp2p/mvds)
 [![Build Status](https://travis-ci.com/vacp2p/mvds.svg?branch=master)](https://travis-ci.com/vacp2p/mvds)
 
-Experimental implementation of the [minimal viable data sync protocol specification](https://specs.vac.dev/mvds.html) including the [metadata format specification](https://specs.vac.dev/mdf.html).
+Experimental implementation of the [minimal viable data sync protocol specification](https://specs.vac.dev/specs/mvds.html) including the [metadata format specification](https://specs.vac.dev/specs/mdf.html).
 
 ## Usage
 

node/node.go

@@ -728,6 +728,6 @@ func (n *Node) insertSyncState(groupID *state.GroupID, messageID state.MessageID
 
 func (n *Node) updateSendEpoch(s state.State) state.State {
 	s.SendCount += 1
-	s.SendEpoch += n.nextEpoch(s.SendCount, n.epoch)
+	s.SendEpoch = n.nextEpoch(s.SendCount, n.epoch)
 	return s
 }