Track hooks on each method

[yangchristian]

Right now, to completely unhook a method, we have to make a call to Collection.unhook() for each time we hooked that particular method with Collection.pre() or Collection.post(). This is because the underlying hooker module just rewraps a hooked function each time it gets hooked.

We could either:

• Write our own hooking library/use a different one
  • Unfortunately, the popular hooks-js (and forks) don't hook correctly onto instances that are also constructors, such as Collection instances (which is a known issue: Hooks for static methods? bnoguchi/hooks-js#14, cause is this line always preferring the prototype)
• Keep a hook count and have unhook() call the underlying hooker.unhook() that many times

[yangchristian]

No more hooks (we have now have Events)