Now only one instance of Tick() can run at a time
Add MessageSender to state struct and CreateState
organization
Merge branch 'master' of github.com:Siacoin/Sia into communication
resolve merge conflict
test heartbeat marshalling
switch AddParticipant to accepting a participant object
added ZeroNetwork to common, a dud network
change participants and add non-nil network objects
adjust how heartbeat announcements get made
touch up testing
added and tested SignedHeartbeat marshalling
add message handling for SignedHeartbeat
start a main, which will contain the demo
Add Identifier type
use Identifiers in TCPServer
add AddMessageHandler method to TCPServer
use Identifier and AddMessageHandler in node tests
move map initialization to InitServer
use NewTCPServer instead of InitServer