Use Persistent wrapper to prevent GC of input Buffer #152

Avoids memcpy of input and output Buffer objects

Improves Buffer and Stream performance by ~3%

test/bench/package.json

@@ -8,12 +8,12 @@
     "test": "node perf && node random && node parallel"
   },
   "devDependencies": {
-    "async": "^1.4.2",
+    "async": "^1.5.0",
     "benchmark": "^1.0.0",
-    "gm": "^1.20.0",
+    "gm": "^1.21.0",
     "imagemagick": "^0.1.3",
     "imagemagick-native": "^1.8.0",
-    "jimp": "^0.2.8",
+    "jimp": "^0.2.19",
     "lwip": "^0.0.8",
     "semver": "^5.0.3"
   },

test/leak/sharp.supp

@@ -278,11 +278,18 @@
   ...
   fun:vips__magick_read_header
 }
+{
+  cond_magick_is_palette_image
+  Memcheck:Cond
+  fun:IsPaletteImage
+  ...
+  fun:get_bands
+}
 
 # glib g_file_read_link
 # https://github.com/GNOME/glib/commit/49a5d0f6f2aed99cd78f25655f137f4448e47d92
 {
-  leak_magick
+  leak_g_file_read_link
   Memcheck:Leak
   match-leak-kinds: definite,indirect,possible
   ...