We also now use the graph DB's own optional functions. An instance of
the graph is currently still passed to the channeldb's
`CreateWithBackend` function. This will be removed in a later commit
once the two have been completely disjoint.
The routing package implements authentication+validation of channel
announcements, pruning of the channel graph, path finding within the network,
sending outgoing payments into the network and synchronizing new peers to our
channel graph state.
Installation and Updating
$ go get -u github.com/lightningnetwork/lnd/routing