fix(Wallet): bind contexts

Some methods weren't being bound, which caused problems when passing the callbacks to different contexts.

Author: mappum

lib/wallet.js

@@ -182,8 +182,7 @@ Wallet.prototype._update = function () {
     this.chain.getBlockAtTime(this.state.createdAt - TIME_MARGIN, function (err, block) {
       if (err) return self._error(err)
       self.state.tip = block
-      self._saveState()
-      self._scanChain()
+      self._saveState(self._scanChain.bind(self))
     })
     return
   }
@@ -201,7 +200,7 @@ Wallet.prototype._scanChain = function (opts) {
     if (err) return self._error(err)
 
     if (path.remove.length > 0) {
-      async.eachSeries(path.remove, self._unprocessBlock, function (err) {
+      async.eachSeries(path.remove, self._unprocessBlock.bind(self), function (err) {
         if (err) return self._error(err)
         processTransactions()
       })