Fix the flip examples

Resolves #337

snippets/flip.md

@@ -10,9 +10,9 @@ const flip = fn => (...args) => fn(args.pop(), ...args)
 let a = {name: 'John Smith'}
 let b = {}
 const mergeFrom = flip(Object.assign)
-let mergePerson = mergeFrom.bind(a)
+let mergePerson = mergeFrom.bind(null, a)
 mergePerson(b) // == b
 b = {}
 Object.assign(b, a) // == b
 */
-```
+```