fix(response.write): handle optional arguments

Author: fernandolguevara

index.js

@@ -80,6 +80,11 @@ function compression (options) {
         return false
       }
 
+      if (!cb && typeof encoding === 'function') {
+        cb = encoding
+        encoding = undefined
+      }
+
       if (!this._header) {
         this._implicitHeader()
       }
@@ -94,6 +99,11 @@ function compression (options) {
         return false
       }
 
+      if (!cb && typeof encoding === 'function') {
+        cb = encoding
+        encoding = undefined
+      }
+
       if (!this._header) {
         // estimate the length
         if (!this.getHeader('Content-Length')) {
@@ -113,7 +123,7 @@ function compression (options) {
       // write Buffer for Node.js 0.8
       return chunk
         ? stream.end(toBuffer(chunk, encoding), encoding, cb)
-        : stream.end()
+        : stream.end(cb)
     }
 
     res.on = function on (type, listener) {