use async writes.

lib/bcoin/chain.js

@@ -816,6 +816,10 @@ ChainDB.prototype.cache = function cache(entry) {
 };
 
 ChainDB.prototype.get = function get(height) {
+  return this.getSync(height);
+};
+
+ChainDB.prototype.getSync = function getSync(height) {
   var data, entry;
 
   if (this._cache[height])
@@ -889,6 +893,10 @@ ChainDB.prototype.getAsync = function getAsync(height, callback) {
 };
 
 ChainDB.prototype.save = function save(entry) {
+  return this.saveAsync(entry);
+};
+
+ChainDB.prototype.saveSync = function saveSync(entry) {
   var self = this;
   var raw, offset;
 
@@ -902,7 +910,6 @@ ChainDB.prototype.save = function save(entry) {
   return this._write(raw, offset);
 };
 
-// This causes weird race conditions with size/count/tip.
 ChainDB.prototype.saveAsync = function saveAsync(entry, callback) {
   var self = this;
   var raw, offset;