Call an action when user is authenticated

[jakubmikita]

We cannot determine when the user has been actually authenticated after the second factor.

We cannot hook into the wp_login nor set_logged_in_cookie as this plugin is hooking into this action to remove authentication cookie and present the second factor form.

[kasparsd]

This looks great, thank you for the contribution @Kubitomakita!

Could you please document the hook in the readme file? Maybe extend the Description section of the readme with a sub-section "Hooks & Filters":

= Actions & Filters =

Here is a list of action and filter hooks provided by the plugin:

- `two_factor_user_authenticated` action which receives the logged in `WP_User` object as the first argument for determining the logged in user right after the authentication workflow. 

[jakubmikita]

Sure thing @kasparsd! Just added

[kasparsd]

@Kubitomakita Looks like phpcs found the following issue:

/class-two-factor-core.php:648:1: error - Whitespace found at end of line (Squiz.WhiteSpace.SuperfluousWhitespace.EndLine)

Could you please fix that?

[jakubmikita]

I'm sorry, saw the Travis failed but couldn't see the error in the log... now everything's ok.