Validate deeply nested properties

## Enable validation of deeply nested properties
Use a string with dot notation or bracket notation to perform validations on complex objects.

```javascript
   var attributes = {
      name: "Nicklas Ansman",
      email: "nicklas@ansman.se",
      deeply: {
        nested: {
          variable: "hello"
        }
      }
    };
    var constraints = {
      name: {
        pass: true
      },
      email: {
        pass: true,
        fail: true,
        fail2: true
      },
      "deeply.nested.variable": {
        fail2: true
      }
    };

    expect(validate(attributes, constraints)).toEqual({
      email: [
        "Email must be a valid email address",
        "Email is simply not good enough"
      ],
      "deeply.nested.variable": [
        "Deeply.nested.variable is simply not good enough"
      ]
    });
```
Nice, tests for utility functions too! :)