Fixes postgres driver not returning numbers for number columns

Rollbacks Model.find() test to avoid casting. Postgres probably does
this because of the number limitation in javascript, but for now we
will always cast it.
Exposes Model methods to change hooks after model definition

Example:

```js
var Model = db.define("...", {
});
Model.beforeRemove(function (next) { // sets hook
    // ....
});
Model.beforeRemove(); // removes hook
```
Adds test for Model.all(), deprecates old one