New node methods for tools and otherwise (#265)

* Add IpfsDHT.{Bootstrap{Random,Self},Peer{Id,Key}}
* Include client mode tests, support for Ping, and uncruft setupDHTs
* Include xerrors in deps

dht_bootstrap.go

@@ -170,3 +170,12 @@ func (dht *IpfsDHT) runBootstrap(ctx context.Context, cfg BootstrapConfig) error
 		return err
 	})
 }
+
+func (dht *IpfsDHT) BootstrapRandom(ctx context.Context) error {
+	return dht.randomWalk(ctx)
+}
+
+func (dht *IpfsDHT) BootstrapSelf(ctx context.Context) error {
+	_, err := dht.walk(ctx, dht.self)
+	return err
+}