Ensure we have nan@^2.0.8

This is to make sure binaries affected by
https://github.com/sass/node-sass/issues/1107 are never built

package.json

@@ -55,7 +55,7 @@
     "glob": "^5.0.14",
     "meow": "^3.3.0",
     "mkdirp": "^0.5.1",
-    "nan": "^2.0.5",
+    "nan": "^2.0.8",
     "npmconf": "^2.1.2",
     "pangyp": "^2.3.0",
     "request": "^2.61.0",