Always use readable-stream/lazystream (#2)

lib/lazystream.js

@@ -1,6 +1,5 @@
-
 var util = require('util');
-var PassThrough = require('stream').PassThrough || require('readable-stream/passthrough');
+var PassThrough = require('readable-stream/passthrough');
 
 module.exports = {
   Readable: Readable,
@@ -29,10 +28,8 @@ function Readable(fn, options) {
 
   beforeFirstCall(this, '_read', function() {
     var source = fn.call(this, options);
-    var that = this
-    source.on('error', function(err) {
-      that.emit('error', err)
-    })
+    var emit = this.emit.bind(this, 'error');
+    source.on('error', emit);
     source.pipe(this);
   });
 
@@ -47,10 +44,8 @@ function Writable(fn, options) {
 
   beforeFirstCall(this, '_write', function() {
     var destination = fn.call(this, options);
-    var that = this
-    destination.on('error', function(err) {
-      that.emit('error', err)
-    })
+    var emit = this.emit.bind(this, 'error');
+    destination.on('error', emit);
     this.pipe(destination);
   });