Yet another strong params support

Inspiration taken from https://github.com/ryanb/cancan/pull/958, https://github.com/ryanb/cancan/pull/911, and others.

This adds strong parameters support but with some smart defaults. Since strong_parameters really only affects cancan for `:create` and `:update` actions, we only apply params for those actions. Further more, by default, we try to run several methods in order:

* `create_params` or `update_params` (depending on the action you are requesting, allows you to override the following other methods if you have different params for creating and updating the resource)
* `<model_name>_params` such as ability_params (the default rails 4 convention when naming your param method)
* `resource_params` (a generically named method... so you don't have to change the method name if you change your model name or cancan key)

Further more, you can specify a custom method to run via the `param_method` option:

`load_and_authorize_resource param_method: :my_sanitizer`

It is also backwards compatible as if none of the methods are found it will carry on with the legacy way.

I've updated the readme and changelogs if we ever get a 1.6.11.